Differential Diagnosis in Radiology Satish K Bhargava, Sumeet Bhargava
Chapter Notes

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Anatomy of Thoracic Inlet
  • Thoracic inlet/root of neck is a narrow space that serves as a junction between the neck and the thorax
  • Boundaries are:
    First thoracic vertebra
    First ribs.
  • This area is further delineated by Sibson's fascia which extends from the transverse process of C7 vertebra to the medial border of first rib
  • Plane of the thoracic inlet is tilted downward anteriorly and laterally on either side being highest medially and posteriorly (Fig. 1.1).
Differential Diagnosis of Lesions at Thoracic Inlet
  1. Congenital lesions:
    Cervical extension of mediastinal thymus
    Thymic cyst
    Vascular anomalies.
    zoom view
    Fig. 1.1: Thoracic inlet
  2. Inflammatory lesions:
    Inflammatory adenopathy—tuberculosis, mononucleosis, HIV infection, etc.
    Cervical abscess
    Tubercular spondylitis with abscess
    Retropharyngeal abscess with mediastinal extension.
  3. Benign tumors:
    Schwannomas and neurofibromas
  4. Malignant tumors:
    Thyroid carcinoma
    Pancoast's tumor
    Lymph node metastasis
    Metastasis to thoracic vertebra and ribs.
  5. Traumatic lesions:
    Esophageal foreign body
    Cervicothoracic hematoma.
  6. Miscellaneous:
    Cervical rib (Fig. 1.2)
    • Thoracic outlet syndrome
    • Intrathoracic goiter (Fig. 1.3).
Develops from congenital obstruction of lymphatic drainage.
Tends to surround and invade normal anatomical structures.
zoom view
Fig. 1.2: Anteroposterior radiograph of cervical spine shows cervical rib arising from C7 on the left side forming pseudoarthrosis with left first rib
Five percent occur in neck (posterior triangle); 3–10% extends into mediastinum, asymptomatic and painless masses, 90% detected by two years of age.
zoom view
Fig. 1.3: Anteroposterior radiograph of chest shows superior mediastinal widening caused by enlarged thyroid gland with a large calcification in its right lobe
Imaging: Multilocular trans-septal masses of fluid attenuation, walls of septa-enhance (if history of surgery/infection). Occasionally hemorrhagic areas and fluid-fluid levels are present.
Benign masses composed of proliferating endothelial cells characteristically increase in size and gradually involute. It most commonly occurs in the first year of life.
Imaging: Calcified phleboliths within the mass may be present. Enhance with adjacent vascular structure and fill with contrast over a short time.
MRI: Intermediate SI on T1WI and high SI on T2WI, fatty replacement may be present.
Cervical Extension of Mediastinal Thymus
  • Due to incomplete mediastinal descent and manifests as solid midline thymus at thoracic inlet
  • Diagnosis is made on the basis of homogenous SI similar to that of the thymus with all MR imaging sequences or connection to the normally located thymus.
Thymic Cyst
  • Caused by persistence or degeneration of the thymopharyngeal ducts
  • 50% of cervical thymic cysts are continuous with mediastinal masses. Most commonly seen on the left side.
Computed Tomography (CT): Well-marginated, unilocular/multilocular, attenuation is close to water.
Magnetic Resonance (MR): Decrease SI on T1WI and intermediate/high SI on T2WI.
  • SI on T1WI may increase if cyst contains blood/protein.
  • Then septa may be present
  • When these cysts occur in the neck, they are located partially within the carotid sheath
  • Most thymic cysts are congenital but they have also been reported with infection, neoplasms, radiation therapy, trauma and thoracotomy.
Vascular Anomalies
  • Venous malformations and AVM are rarely seen in the neck
  • Jugular vein thrombosis occurs after placement of a central catheter or in association with compressive lesion and is seen as luminal obstruction with thin rim of enhancement of the vasa vasorum
  • Cervical aortic arch—High-positioned, usually right-sided aortic arch. Occasionally associated with other cardiac and vascular anomalies, patient presents with respiratory problems/ dysphagia
  • A pulsatile mass is found in the neck.
Cervical Abscess
  • Cervical abscesses seldom cross the thoracic inlet into the mediastinum
  • Infection in the visceral space may extend into the anterior mediastinum, whereas infection in the retropharyngeal and prevertebral spaces may extend into the posterior mediastinum.
Imaging is required to distinguish cellulitis and suppuration adenopathy from the abscesses which require surgical treatment. In suppuration-focal hypoattenuating mass with an enhancing rim on CECT and a complete hypoechoic to anechoic mass with a variable thick rim of solid tissue is seen on ultrasound scans. In fluid collection—SI on MR varies according to protein content, skin thickening and reticulated fat planes may be seen adjacent to the abscess margins in CT and MR.
Tuberculous Spondylitis with Abscess Formation
  • Infection usually starts anteriorly in the vertebral body
  • In 90% cases, at least two vertebrae are affected
  • Skip lesions occur in 4% cases
  • Paraspinal abscesses are present in 55–90% cases
  • Imaging features:
    • Vertebral body destruction
    • Loss of disc space
    • Paraspinal abscess
    • Prevertebral and epidural collections
    • Paraspinal calcification.
  • In the neck—dysphagia, hoarseness and lymphadenopathy are the accompanying features.
Retropharyngeal Abscess with Mediastinal Extension
Causes of Retropharyngeal Abscess
  • Tonsillar infection
  • Iatrogenic/traumatic
  • Perforation of pharynx.
X-ray neck soft tissue: Retropharyngeal soft tissue thickening, forward displacement of airway.
CT/MR: Retropharyngeal collection continuing into the post-mediastinum through the thoracic inlet.
  • Most common cervical neoplasms of mesenchymal origin
  • Typically present as painless slowly-growing masses, most commonly occurring in posterior triangle.
CT: Homogeneous non-enhancing mass, isodense with subcutaneous fat, usually well-encapsulated lesions (−10 to −100 HU).
MRI: SI similar to subcutaneous fat (increase on T1WI, intermediate SI on T2WI and loss of SI on fat suppressed MR images).
Rare, usually encapsulated benign neoplasm of the embryonal fat. Composed of mature and immature fat and found almost exclusively in infants (90% <3 years) and children.
Most common site—Extremities → trunk → head → neck.
CT: Fat separated by septa of soft tissue which does not enhance.
MR: Heterogeneous and have intermediate to high SI on T1WI according to the amount of immature fat. On fat suppressed images—area of high SI is suggestive lipoblastoma.
Schwannomas and Neurofibromas
  • Common sites are—vagus nerve, ventral and cervical nerve roots, cervical sympathetic chains and brachial plexus
  • Plexiform neurofibromas are pathognomonic of Type I neurofibromatosis.
CT: Hypo to isoattenuating at CT. Contrast enhancement is more often seen with schwannomas.
MR: Low to intermediate SI on T1WI and intermediate to high SI on T2WI. They show non-uniform enhancement. Plexiform neurofibromas usually involve cartilaginous soft tissue.
  • Malignant degeneration is seen in 15–30% cases
  • Tumors arising in vagus nerve displace the common carotid and internal carotid arteries. Anteromedially and the internal jugular vein posterolaterally
  • Sympathetic chain tumors demonstrate a constant relationship with the longus colli muscle
  • Brachial plexus tumors displace the anterior scalene muscle anteriorly.
Aggressive Fibromatosis
  • Characterized by proliferation of fibrous tissue with locally aggressive behavior and a tendency toward recurrence after resection
  • Etiology is unknown
  • Appearance on MR is often infiltrative and can suggest malignancy. Usually has decreased SI on T1 and T2WI that permits diagnosis.
  • Hodgkin's disease accounts for majority of lymphomatous anterior mediastinal masses and the neoplastic cells typically infiltrate the thymus
  • Thymic involvement is always accompanied by involvement of mediastinal lymph node
  • Lymphoma of neck involves cervical lymph node chain, Waldeyer's tonsillar ring and lymphoid tissue at the base of tongue. Such lymphoma is most often of the non-Hodgkin's type
  • Calcification and necrosis can be seen if lymphoma was treated previously.
Thyroid Carcinoma
  • Papillary carcinoma accounts for 75–90% of all the cases and is especially prevalent in younger patients
  • Medullary, follicular and anaplastic carcinoma account for 10–25%
  • Usually evaluated by ultrasound or scintigraphy. CT/MR is required to evaluate tumoral extent when malignant tumors are suspected
  • Difficult to distinguish benign from malignant nodule because the findings are non-specific. However, thyroid masses with infiltrating margins that obscure soft tissue plane and associated with adenopathy are suggestive of carcinoma
  • Cold nodules on scintigraphy have a higher frequency of malignancy
  • MR is preferred as compared to CT because iodine administered during CT can cause iodine 131 therapy to be postponed for up to 6 months after the removal of maximum tumor volume.
  • 10–15% neuroblastomas are located in posterior mediastinum. More than 5% neuroblastomas arise in the neck
  • Arise from the renal cell rest blasts located in the adrenal gland or sympathetic chain
  • Osteochondritis and ipsilateral Horner's syndrome are related to lesion of cervical sympathetic nerve
  • 50% neuroblastoma shows calcification on X-ray
  • 90% show calcification on CT
  • MR imaging is the modality of choice for demonstrating the full extent of mass, chest wall invasion and extra-adrenal intraspinal involvement
  • Lymph nodes involved are deep cervical lymph nodes along the internal jugular vein, supraclavicular lymph node, scalene nodes, and highest lymph node in superior mediastinum.
Pancoast's Tumor
  • Pancoast's syndrome consists of a constellation of signs and symptoms that include shoulder and arm pain in the distribution of C8, T1 and T2 nerve roots, Horner's syndrome and atrophy of hand muscle
  • This is caused by tumor in lung apex (squamous cell carcinoma) which is causing invasion of the chest wall, and prevertebral sympathetic chain or the inferior or stellate ganglion
  • This tumor should be ruled out if unilateral pleural thickening or asymmetric thickening > 5mm is noted on chest X-ray.
Metastases: (to rib and thoracic vertebra).
  • Usually has a mixed pattern: Breast/lung
  • Blastic—Prostate
  • Lytic—Thyroid, kidney
  • Vertebra—Pedicles and vertebral body are involved
  • Ribs—Lesions are recognized early when the rib is expanded.
Air can travel from the mediastinum along the fascial planes to the neck; subcutaneous tissue and chest wall.
Most common causes in children are asthma, aspiration of foreign body and trauma.
11Esophageal—foreign body granuloma.
  • Most commonly seen in infants and children
  • Most common site of retention is the upper esophagus at the thoracic inlet
  • Long standing foreign body produces a granulomatous tissue reaction that manifests as a mass
  • Mediastinitis and abscess can be seen in this region as a complication of foreign body perforation.
Cervicothoracic Hematoma
  • Trauma
  • Faulty placement of central catheter
  • Hematomas are usually trans-spatial lesions.
Computed Tomography (CT)
  • Hyperdense in acute phase
  • Hypodense in chronic phase and on MR SI varies depending on the phase.
Cervical Rib
  • Seen in 1% of population
  • Symptomatic in 10%
  • Unilateral in 50–80%
  • Cervical ribs vary in length and may be connected to the first rib by a fibrous band
  • Cervical rib may affect the brachial plexus in any one of the following two ways:
  1. May narrow the space between the posterior aspect of first rib and anterior scalene muscle through which the nerve and subclavian artery passes.
  1. Cervical rib may be situated such that a portion of the brachial plexus must pass over it, thereby stretching the lower trunks.
    • Results in cervical rib syndrome—Sensory symptoms usually antedate motor involvement and occur along the ulnar border of forearm and hand
    • Muscle wasting of Thenar eminence.
Thoracic Outlet Syndrome
Because of compression of the subclavian artery and C8/T1 nerve.
Usual Causes
  • Cervical rib
  • Elongated transverse process of C7
  • Fibrous band extending from transverse process of C7 to the first rib
  • Low set shoulder girdle
  • Pancoast's tumor.
Intrathoracic Goiter
Characterized by:
  • Continuity with cervical thyroid gland
  • Marked enhancement on CECT
  • Well-defined margins
  • Inhomogeneity
  • Focal calcification.
Detected by two years of age and seen to extend from posterior triangle multilocular cystic mass.
Thymic Cyst
Unilocular/multilocular cystic mass seen in continuation with thymus.
Cervical Abscess
Hypodense collection with enhancing rim with adjacent reticulated fat plane.
Pott's Spine with Abscess
Vertebral body destruction with loss of IVD space with adjacent collection and calcification.
  • Painless progressive mass, well-encapsulated isointense to fat.
  • Fast growing; adults
  • Soft tissue admixed with fat.
  • 90% <3 years
  • Areas of increase SI on T2WI
  • Fat separated by septa.
zoom view
Flow chart 1.1: Lesions of thoracic inlet
Schwannoma and Neurofibroma
  • Plexiform neurofibroma associated with neurofibroma.
  • Arises from sympathetic chain
  • Children
  • Calcification present in 90%
  • Horner's syndrome.
Thyroid Carcinoma
  • Mass is contiguous with thyroid and has infiltrating margins and obscures soft tissue plane.
Pancoast's Tumor
Mass lesion in lung apex with destruction of first rib.
  • Patient presents with Pancoast's syndrome.
Metastatic Lymph Node Mass
Primary lesion can be localized.
  • Compressible mass lesion, multiple small cystic spaces, phlebolith is present, vascular enhancement is present.
Cervical Rib
Extra rib is seen to arise from transverse process of C7.
Anterior mediastinal masses
Thyroid Tumor (Table 1.2):
  1. Non-toxic enlargement of the gland.
  2. Thyrotoxicosis.
  3. CA thyroid.
  4. Hashimoto's disease.
Thymic Tumors
Normal thymic shadow
Triangular soft tissue mass that projects to one side of the mediastinum.
  • On expiratory film
  • Slightly rotated film
  • Severe neonatal infection
  • After major surgery
  • Use of steroids.
Commonest Tumors of Mediastinum (Table 1.1)
  1. Thymoma
    1. Benign
    2. Malignant 30%.
  2. Hyperplasia of the gland.
  3. Thymic cyst.
  4. Thymolipoma.
  5. Lymphoma.
  6. Germ cell tumor.
  7. Carcinoids.
Teratodermoid Tumors
  • Dermoid cyst
  • Teratoma
    • Benign
    • Malignant
  • All arise from the primitive germ cell nests in the urogenital ridge
  • Dermoid cyst contains mainly ectodermal tissues.
    Table 1.1   Tumors of mediastinum (both common and rare)
      • Tortuous innominate artery
      • Lymph node
      • Retrosternal goiter
      • Fat deposition
    • Innominate artery aneurysm
    • Parathyroid adenoma
    • Lymphangioma
      • Lymph node enlargement
      • Aneurysm of ascending aorta
      • Thymoma
      • Teratoma
    • Sternal mass
    • Lipoma
    • Hemangioma
      • Epicardial fat pad
      • Diaphragmatic hump
      • Pleuropericardial cyst
    • Morgagni hernia
      • Lymph node enlargement
      • Aortic arch aneurysm
      • Enlarged pulmonary artery
      • Dilatation of SVC
      • Bronchogenic cyst
    • Tracheal lesion
    • Cardiac tumor
      • Neurogenic tumor
        Pharyngoesophageal pouch
      • Aneurysm of descending aorta
      • Esophageal dilatation
      • Azygous dilatation
      • Hiatus hernia
    • Neurenteric cyst
    • Pancreatic pseudocyst
    • Sequestrated lung
      • Neurogenic tumor
      • Paravertebral mass
    • Bochdalek hernia
    • Extramedullary hemopoiesis
  • Solid teratoma contains tissues of ectodermal, mesodermal and endodermal origins.
Dermoid cyst appears as a round or oval soft tissue mass, which may show peripheral rim or central nodular calcification. A fat fluid level or a rudimentary tooth is diagnostic radiological sign. Teratoma appears as a lobulated soft tissue mass which on CT shows a mass of mixed attenuation containing soft tissue, cyst fluid, fat, calcification of bone.
  • Anterior mediastinal mass
  • 75% occur in right anterior cardiophrenic angle
  • Cysts have thin walls, which contain clear fluid
  • These change shape with respiration.
Table 1.2   Differential diagnosis of retrosternal goitre
Non-toxic enlargement of thyroid
CA thyroid
Hashimoto's disease
  1. Vocal cord involvement
  1. SVC compression
  1. Calcifcation
  1. Rapid increase in size
Hemorrhage cyst
  1. Symptom severity
Clinical manifes-tation
  1. Orbital lesion
Morgagni Hernia
  • Persistent developmental defect in the diaphragm anteriorly.
  • Anterior mediastinal mass.
  • May contain omentum or transverse colon.
  • Appears as a soft tissue mass
  • Containing either gas or air-fluid level or fat.
  • Diagnosis is confirmed by barium meal and follow through or barium enema.
Lymph Node Enlargement
Metastatic (Table 1.3)
  • Intrathoracic:
    • Bronchial CA
    • Esophageal CA.
  • Extrathoracic:
    • Breast, renal
    • Adrenal, testicular
    • Tumors of pharynx and larynx.
Table 1.3   Metastatic lymph nodes
Head and neck squamous cell carcinoma
Renal cell carcinoma
Breast carcinoma
Mucinous adenocarcinoma of GIT
Nasopharyngeal carcinoma
Thyroid carcinoma
Small cell carcinoma of lung
Ovarian and prostate carcinoma
Table 1.4   Differential diagnosis of soft tissue lesions in right anterior cardiophrenic angle
Change shape with respiration
Separate from pericardium
Silhouette sign
  1. Pleuropericardial cyst
Soft tissue
  1. Epicardial fat pad
  1. Partial eventration of right hemidia-phragm
Soft tissue
Diaphragm contour
  1. Right middle lobe pathology
Soft tissue
  1. Morgagni hernia
Fat if Omentum +
  1. Right atrial tumor
Soft tissue
Soft tissue
  1. Pericardial lesion
Soft tissue fluid
  • Lymphoma
  • Leukemia
  • Sarcoidosis: Bilateral hilar masses with well-defined outline. These show egg shell calcification
  • Primary tuberculous infection produces an area of consolidation in one of the lobes with unilateral hilar mass and an associated pleural effusion
  • Low attenuation areas due to cyst formation or necrosis are seen in lymph nodes involved with Hodgkin's disease and metastatic testicular or squamous cell tumors, particularly after treatment with radiotherapy or chemotherapy.
Aortic Aneurysm (Fig. 1.4)
This produces either widening of the mediastinum or a round or oval soft tissue mass in any part of the mediastinum with a well-defined outline.
zoom view
Fig. 1.4: Posteroanterior radiograph of chest shows aneurysm of arch of aorta. Incidental note is made of the fibrotic changes in the left upper lobe
Curvilinear or peripheral calcification may be due to syphilitic aortitis or atherosclerosis. It may cause pressure erosion defect of the sternum or anterior scalloping of one or two vertebral bodies. The subintimal flap and false lumen of a dissecting aneurysm can be demonstrated by CT.
Tortuous Innominate Artery
It occurs in 20% of the elderly patients with hypertension and produces widening of the superior part of the mediastinum on the right without displacement of the trachea to the left.
Bronchogenic Cyst
  • Middle or posterior mediastinal mass
  • Majority occur around the carina in the paratracheal, tracheobronchial or subcarinal region
  • Can alter in shape on respiration
  • Pericardial defect may occur in association.
Tracheal Tumors
Tracheal tumors include carcinoma, plasmacytoma. They narrow the tracheal lumen and appear as soft tissue mass.
Neurogenic Tumors (Table 1.5)
Table 1.5   Neurogenic tumors
Central spicules or peripheral rim
  • These may be asymptomatic or may produce back pain and may even extend through an intervertebral foramen into the spinal canal (dumb-bell tumors) to produce spinal cord compressions
  • Involvement of the posterior ribs or adjacent thoracic vertebrae—produce ribs splaying, localized pressure erosion defect of one or two vertebral bodies and ribs notching.
  • Commonest cause of a mediastinal mass on a chest radiograph in an elderly patient. It appears as a soft tissue mass with an air-fluid level
  • Lies to the left of the midline
  • Contents could be liver, omentum and small intestine.
Present with dysphagia.
Pharyngoesophageal pouch: Soft tissue mass with an air-fluid level, lies in the midline, displaces trachea forward.
Carcinoma/leiomyoma: Soft tissue mass with an air-fluid level, behind the heart.
Achalasia: Large soft tissue mass with air-fluid level with barium flowing in spurts. Pulmonary consolidation/bronchiectasis may be present.
Involves the thoracic vertebrae or intervertebral disk space. They appear as an elongated or lobulated soft tissue mass with a well-defined outline.
Differential diagnosis would be:
  • Hematoma
  • Pyogenic abscess
  • Tubercular abscess
  • Multiple myeloma
  • Lymphoma
  • Metastasis
  • Extramedullary hematopoiesis.
Bochdalek Hernia
  • Its persistency develops mental defect in the diaphragm posteriorly
  • Occurs in the left hemidiaphragm
  • Small hernias usually contain retroperitoneal fat, kidney or spleen, that appear as a soft tissue mass in the posterior costophrenic angle
  • Larger hernias may contain jejunum, ileum and colon.
Neurenteric Cysts
Result due to partial or complete persistence of the neurenteric canal or its incomplete resorption includes gastro-intestinal duplication, enteric cyst, neurenteric cyst, anterior meningocele and cysts of the canal.
Pancreatic Pseudocyst
  • Posterior mediastinal mass
  • Round/oval soft tissue mass behind the heart
  • A left basal pleural effusion or atelectasis in the lower lobes may result
  • Extramedullary hemopoiesis
  • Appears as lobulated paravertebral soft tissue mass behind the heart.
  1. Trachea and esophagus.
  2. Muscles—sternohyoid, sternothyroid and lower ends of longus colli.
  3. Anterior arch of aorta, brachiocephalic artery, ICC and left subclavian artery.
  4. Veins—right and left brachiocephalic vein, upper-half of SVC.
  5. Nerves—vagus, phrenic, cardiac nerve, right laryngeal nerve.
  6. Thymus.
  7. Thoracic duct.
  8. LNs—paratracheal, brachiocephalic, tuberculosis.
Criteria for Superior Mediastinum Widening
>8 cm in the transverse diameter.
>25% of the thoracic diameter at that level.
  1. Retrosternal goiter: Less than 5% of enlarged thyroid in the neck. Extend into mediastinum due to non-toxic enlargement, thyrotoxicosis, carcinoma, Hashimoto's disease (Table 1.3).
    • Soft tissue swelling that moves on swallowing
    • Dysphagia, stridor if benign, vocal cord paralysis or SVC compression-malignancy
    • Patients present soft tissue mass in anterior part; extend down from the neck
    • Outline well-defined in mediastinum but fades off into the neck
    • Displacement and compression of trachea to the left, 20% are retrotracheal
      zoom view
      Fig. 1.5: Boundaries of superior mediastinum
    • Ca++ nodules, linear or crescent pattern
    • CT mass of mixed attenuation extending from one of the lower poles of thyroid
    • Radionuclide scan 99 Tc pertechnetate on 123I NaI
    • MRI – Diagnostic.
  2. Thymus—Normal thymus—most common in infants
    • Most common in adult benign and malignant thymoma
    • Associated with myasthenia gravis, red cells aplasia or decreased granulocytes
    • Plain X-ray chest –ve
    • CT - Grossly asymmetrical lobular configuration.
      • Homogenous with mild contrast enhancement.
      • Less commonly decreased attenuation areas—Hemorrhage/necrosis/cyst Ca++ occasionally.
    • MRI = T1 = Med. SI, T2 ⇒ fat
Thymic hyperplasia
    • Seen in 2/3rd of myasthenia gravis
    • CT = symmetric diffuse enlargement
    • MR = same signal as normal gland
    • Enlargement of thymus may also be seen in thymic cyst, thymolipoma, lymphoma, germ cell tumor and carcinoid.
    • Teratodermoid tumors/germ cell tumor—Extra-gonadal germ cell tumor located within or adjacent to thymus
    • Most common germ cell tumor in superior mediastinum is dermoid cyst and benign and malignant teratoma. Chest radiograph (CXR) may show round or oval soft mass with well-defined border and may contain peripheral rim or central nodules of Ca++.
    • III On CT, fat fluid level, Ca++ calcifications, well-defined border and soft tissue attenuation mass is highly suggestive of germ cell tumor.
    • Malignancy – more solid component and aggressive features.
    • Lymph node enlargement (Fig. 1.5)
    • Widened mediastinum may have lobulated margins in case of LN enlargement
    • Hodgkin/Non-Hodgkin disease—paratracheal and tracheo-bronchial, asymmetrical widening of middle part of superior mediastinum
      • Associated feature—parenchymal lung disease
      • Ca++ in LN seen after irradiation
    • Tuberculosis—Unilateral paratracheal lymphadenopathy without obvious mediastinum or pleural involvement seen in immuno-compromised patients
    • In an adult/children area of consolidation/caseation
    • Fungal disease histoplasmosis, coccidioidomycosis, blastomycosis
      • Enlargement of hila or paratracheal LN
      • Ca++ in healing histoplasmosis
        Sarcoidosis—Bilateral lobulated hilar mass
        zoom view
        Fig. 1.6: PA radiograph of chest shows superior mediastinal widening caused by right paratracheal adenopathy in a case of Koch's chest
  • Primary tumor is usually intrathoracic—Esophagus/Bronchus
  • Benign—in adult
    • Papilloma
    • Chordoma Ca++ smooth, well-defined and fibroma < 2 cm in diameter
    • Hemangioma
  • Mucus plug—decreased alternation, mixed with air and will change in position and resolve after coughing
  • Malignant—squamous cell carcinoma and adenoid cystic Ca2 – Most commonly a smooth or irregular intraluminal mass with asymmetry. Narrowing of tracheal lumen is seen.
  1. Aneurysm and dissection of arch of aorta—true, pseudo, post-traumatic atherosclerotic, post-traumatic elderly, fusiform.
    • Younger, contained by adventitia only, saccular
    • Clinical presentation → Asymptomatic
    • Symptoms—enlarged compresses adjacent structure
    • C × R = Widening with or without Ca++
    • CT = Saccular and fusiform dilatation of segment of aorta
    • –>4cm; use short-axis diameter
    • Ca++ in aortic wall, peripheral
    • Intraluminal thrombus—crescentic/circumferential
    • Displacement of adjacent structure = Trachea, bronchus and pulmonary artery, superior vena cava, esophagus, bony erosion, growth rate 5.6 cm/year
      Aortic dissection emergency situation:
    • Peak 7th–8th decade
    • Most common predisposing condition is hypertension– congenital heart disease, coarctation, bicuspid AV
    • Intimal tear—blood enters into the aortic wall and creates a false and true lumen
    • CXR wide mediastinum aortic contour displaced, intimal Ca++
    • CT = Internal displacement or intimal Ca++
    • Visible internal flap increased in attenuation
    • High density thrombus in false lumen if actue hemorrhage
    • CECT—contrast-filled true and false lumen separated by intimal flap
    • Delayed enhancement of false lumen because of slow flow
    • MR—very well-demonstrate the intimal flap
    • Aortography—Highly accurate.
    • Dilatation of SVC and other veins
    • Dilatation of SVC seen in raised CVP
    • CCF
    • Tricuspid valve disease
    • Mediastinal mass
    • Constrictive pericarditis
    • TAPVD—Supracardiac variety. All the pulmonary veins open into large ascending vein on the left side which is a remnant of embryonic. Left SVC. This connects into the left brachiocephalic vein which then passes into the right-sided SVC and into the RA.
    • A pharyngoesophageal pouch/Zenker's diverticulum
    • CXR = Soft tissue mass in posterior part of superior mediastinum which contains an air-fluid level.
    • Soft tissue mass lies in the midline and displaces the trachea forward
    • Barium-esophagogram—confirm the diagnoses.
    • Fat deposition—superior mediastinum widening and epicardial fat pad seen in obese adult patients, Cushing's disease, steroid therapy
    • CT = shows an excessive amount of mediastinal fat
    • Tracheal mass—positive with non-specific symptoms like cough, dyspnea, stridor, wheezing
    • CXR = Not very helpful
    • Benign – in adult
    • Papilloma
      • Chordoma Ca++
      Smooth well-defined and < 2cm in
      • Fibroma
    • Hemangioma
    • Mucus plug—decrease attenuation, mixed with air and will change in position and resolve after coughing
    • Malignant—Squamous cell carcinoma and adenoid cystic carcinoma are most common
    • A smooth or irregular intraluminal mass with asymmetric narrowing of tracheae lumen is seen.
    • Neurogenic tumor:
    • Adult—NF and schwannoma—peripheral intercostal nerve children—ganglioneuroma and neuroblastoma—which arise is thoracic sympathetic ganglia
    • CXR—A round or oval soft tissue mass in paravertebral gutter which usually project to one side of mediastinum
    • Neuroblastoma—Central spicules or peripheral rim Ca++ splaying of posterior ribs
    • Pressure erosion and defect of vertebral bodies
    • Rib notching
    • Enlargement of an intervertebral foramen
    • CT = solid mass of soft tissue attenuation, may contain Ca++ and involve the adjacent bone
    • MRI = intraspinal extension
    • MRI = transaxial SE
    • GRF/phase velocity mapping.
Anterior mediastinum lies anterior to anterior pericardium and trachea. For ease of differential diagnosis, it can be divided into three areas (Table 1.6).
Salient Features
Region 1 (Fig. 1.7)
  1. Thyroid tumor (Retrosternal goiter)
    • Less than 5% goiters extend into the mediastinum.
    • Mostly females presenting with soft tissue swelling, dysphagia, stridor.
    • Chest X-ray shows oval soft tissue mass in superior part of anterior mediastinum fading off into the neck.
    • Well-defined smooth or lobulated.
    • Central nodular, linear calcification.
    • Displacement and compression of trachea.
      Table 1.6   Differential diagnosis of anterior mediastinal lesion
      Region 1
      Region 2
      Region 3
      • Tortuous innominate artery
      • L N enlargement
      • Epicardial fat pad
      • Lymph nodes
      • Aneurysm of aorta
      • Diaphragmatic hump
      • Retrosternal goiter
      • Thymoma tumors
      • Pleuropericardial cyst
      • Fat deposition
      • Teratodermoid
      • Morgagni's hernia
      • Aneurysm of innominate artery
      • Sternal mass lipoma
      • Parathyroid adenoma
      • Hemangioma
      • Cystic hygroma or lymphangioma
    • CT shows mass of mixed attenuation with cysts and calcifications, contiguous with one of the poles of thyroid.
  2. Lymph node enlargement
    May be due to lymphoma, metastasis or infection.
    • Widening of mediastinum on chest X-ray.
    • Lobulated soft tissue mass due to indentation by ribs.
    • Calcification may be present.
    • Lymphadenopathy elsewhere in the body.
    • CT shows discrete round or slightly irregular densities of various sizes +/− enhancement and necrosis.
  3. Fat deposition
    • Cushing's disease, corticosteroid therapy.
    • Widening of superior mediastinum on chest X-ray.
    • CT shows excessive amount of mediastinal fat with density −50–100 HU.
  4. Tortuous innominate artery or aneurysm
    • Common in elderly.
    • Widening of superior mediastinum.
    • CT shows dilatation of innominate artery.
  5. Lymphangioma/cystic hygroma
    • Mainly in children.
    • Transilluminating soft tissue swelling in the root of the neck.
    • Chest X-ray shows: Oval soft tissue mass extending into the neck.
    • Alters shape on respiration but does not displace trachea.
    • Ultrasound and CT shows cystic septated mass.
  6. Parathyroid adenoma
    • Hypercalcemia with hyperparathyroidism.
    • Usually small with normal chest X-ray.
    • Confirmed by radionuclide scan with 201 Tl chloride with increased activity.
Region 2
  1. Thymoma: Usually adults.
    • Can present with myasthenia gravis (10–15%)
    • Round oval and smooth or lobulated.
      zoom view
      Fig. 1.7: Diagram showing anterior mediastinal masses
    • May have nodular or rim calcification.
    • CT shows mixed attenuation mass with calcification and cysts.
  2. Teratodermoid tumor: Commonly dermoid cysts and benign and malignant teratomas.
    • Anterior mediastinal mass in young adult patient, dyspnea, cough, chest pain.
    • Round or oval soft tissue mass, projects to one side.
    • Calcification, especially rim, fragments of bone and teeth are diagnostic.
    • Fat with fat-fluid level.
  3. Lymph node enlargement.
  4. Aneurysm of ascending aorta
    • Widening of mediastinum or mediastinal mass.
    • Well-defined outline.
    • Peripheral rim of calcification.
    • Pulsatile mass on fluoroscopy.
    • Pressure erosion of sternum.
    • CT shows dilated aorta with blood of higher attenuation.
  5. Sternal mass
    Metastasis, plasmoacytoma, chondrosarcoma, osteomyelitis.
    • Soft tissue mass with sternal destruction.
    • Tumor new bone formation or lytic expansion of sternum.
    • Collection in anterior mediastinum with sternal destruction in osteomyelitis.
  6. Lipomas
    • Round or oval soft tissue density mass with low density.
    • Alters shape on respiration.
    • CT shows solid mass of fatty attenuation.
  7. Hemangioma
    Widening of mediastinum, round or oval soft tissue mass, phleboliths are diagnostic.
Region 3
  1. Epicardial fat pad
    • Especially in obesity.
    • Triangular opacity in cardiophrenic angle.
    • Less dense due to fat.
    • CT shows fat density and is diagnostic.
  2. Diaphragmatic hump
    • Localized eventration.
    • Common on anteromedial portion of right dome.
    • Portion of liver extends into it.
    • Can be confirmed by ultrasound.
  3. Pleuropericardial cyst
    • Spring water cyst or pericardial diverticulum.
    • 75% in Rt. anterior cardiophrenic angle.
    • Round/oval/triangular soft tissue mass.
    • Alters shape on respiration.
    • Ultrasound or CT shows trans-sonic or cystic mass adjacent to pericardium with density 0—20 HU.
  4. Morgagni's hernia
    • 90% in right anterior cardiophrenic angle.
    • Round or oval soft tissue mass.
    • Lower radiographic density than expected for its size.
    • Larger hernias contain transverse colon which appears as soft tissue mass with air-fluid level.
    • Diagnosis by ultrasound, confirmed by barium meal examination or CT.
  • Normal thymus
    • Sail sign +ve
    • Wave sign +ve
    • Notch sign +ve
  • Cystic hygroma
    • Cystic septated mass in neck and mediastinum
  • Morgagni's hernia
    • Soft tissue density in cardiophrenic angle
  • Neoplastic
  • Soft tissue density mass
    • With discrete L.N. +/− enhancement +/− calcification
    • LN elsewhere.
  • With calcifications fat, tooth, cyst
  • Teratodermoid tumor
  • Inflammatory
    • Lymph nodes with rim enhancement
    • Collection or abscess.
Widening of mediastinum on X-ray with lobulated soft tissue density mass on CT.
Multiple discrete or matted LN +/− enhancement, calcification, LN elsewhere.
  • Soft tissue calcification cysts
  • Associated with myasthenia gravis
  • Teratodermoid
  • Cyst calcification
  • Tooth, fat, young adult.
  • Mixed attenuation contiguous with thyroid pole
  • Widening with fat density on CT
  • Epicardial fat pad.
Widening with cystic density
Pleuropericardial cyst
  • Abscess
  • Aortic aneurysm
  • Hemangioma
  • Mass.
  1. Lymph nodes
    • Neoplastic
    • Inflammatory.
  2. Foregut duplication cysts
    • Bronchogenic cyst
    • Esophageal duplication cyst
    • Neurenteric cyst.
  3. Cystic hygroma
  4. Vascular
    • Vena cava enlargement.
  1. Lymph nodes
    • Neoplastic
    • Inflammatory
    • Inhalation disease.
  2. Primary tumors
    • Carcinoma of trachea
    • Bronchogenic carcinoma
    • Esophageal tumor
    • Leiomyoma, carcinoma
    • Mesothelioma.
  3. Vascular lesions
    • Aortic aneurysm
    • Distended arteries or veins.
  4. Bronchogenic cyst.
  • 90% of masses in the middle mediastinum are malignant
  • Paratracheal, tracheobronchial, subcarinal and bronchopulmonary groups. Middle mediastinal lymph node groups
  • Often asymptomatic, may produce cough, dyspnea and weight loss
  • It appears as widening of right paratracheal stripe, bulge in aortopulmonary window, lateral displacement of azygo-esophageal line, lobulated widening of mediastinum and unilateral or bilateral lobulated hilar soft tissue mass.
  • Hodgkin's disease, non-Hodgkin's disease and the lymphatic leukemias produce middle mediastinal lymphadenopathy, which is often unilateral.
Hodgkin's Disease
  • On CT, nodal involvement ranges from enlarged discrete lymph nodes to large conglomerate masses
  • Thymic involvement is seen in 70% of the cases
  • Involvement of superior mediastinal lymph node was seen in 98% of patients with intrathoracic disease.
Non-Hodgkin's Disease
  • Non-contiguous spread, more advanced disease, other sites involvement more common
  • Involvement of superior mediastinum in < 75% cases
  • Parenchymal involvement of lungs also occurs and calcification occasionally develops in Hodgkin's disease after radiation
  • Fungal infections like histoplasmosis, coccidioidomycosis, blastomycosis produce hilar or paratracheal mediastinal adenopathy with or without pulmonary involvement
  • Other infective and inflammatory causes include infectious mononucleosis, measles, whooping cough, mycoplasma, adenovirus and lung abscess.
Inhalation Disease
  • Silicosis—egg-shell calcification
  • Coal worker's pneumoconiosis
  • Berylliosis.
Foregut Duplication Cyst
Bronchogenic cyst—It is a thin-walled foregut cyst lined by ciliated columnar epithelial cells of respiratory origin that contains viscid mucoid material.
  • Usually seen as an incidental mass in a young adult
  • Rarely the cyst can become infected in children and rupture into the bronchial tree and hemorrhage into the cyst can also occur
  • Majority occurs around carina in subcarinal region but can occur in right paratracheal or posterior mediastinum
  • Appear as well-defined round or oval soft tissue mass that can alter in shape on respiration.
Diagnosis is confirmed by CT or MRI. CT shows a thin-walled cyst containing fluid of either low attenuation (0–20 HU) or mucinous material containing cysts (20–50 HU).
Esophageal Duplication Cyst
  • Less common than bronchogenic cysts, usually larger and usually situated to the right of the midline extending into the posterior mediastinum
  • May be incidental finding or produce symptoms related to esophageal or respiratory compression. It may contain ectopic gastric mucosa causing ulceration, hemorrhage or perforation.
Neurenteric Cyst
  • Located in middle or posterior mediastinum
  • Contains neural tissue and maintains a connection with spinal canal
  • Commonly right-sided and associated with vertebral body anomalies like hemivertebrae, butterfly vertebrae, and scoliosis which are usually superior to it
  • CT, MRI—for defining extent, relationship to other structure and defining intrinsic contents that may be watery or viscous.
Cystic Hygroma
  • 5% cases extend into the mediastinum from the neck
  • Mostly present at birth
  • Cystic with septation and some solid components on all imaging modalities.
Thoracic Aortic Aneurysm
  • Usually seen as an incidental mediastinal abnormality on a chest radiograph in elderly patients
  • It appears as either widening of the mediastinum or as a well-defined round or oval soft tissue mass in any part of the mediastinum often with curvilinear calcification in its wall
  • Displacement of rim of calcification—aortic dissection
  • Pressure erosion of sternum or vertebral bodies
  • Diagnosis confirmed by CT or MRI which shows—aorta > 4 cm and containing contrast-enhanced blood in its lumen with surrounding mural thrombus of lower attenuation and calcification in its wall.
Other Arterial Abnormalities
  • Dilatation of the main pulmonary artery due to pulmonary artery hypertension, pulmonary valve stenosis with post-stenotic dilatation or a pulmonary artery aneurysm also produces an apparent left hilar mass
  • A tortuous innominate artery produces widening of the superior mediastinum on the right and an aneurysm of the innominate or subclavian arteries produce widening of the mediastinum on the left, often simulating a left hilar mass.
Venous Abnormality
  • Dilated superior vena cava produces slight widening of the mediastinum on the right usually caused by congestive, cardiac failure, tricuspid valve disease, etc.
  • A persistent left-sided superior vena cava produces slight widening of the mediastinum on the left side
  • A dilated azygous vein—oval soft tissue mass in the right tracheobronchial angle.
  • Most mediastinal lymph node metastases arise from a primary thoracic neoplasm, most commonly bronchogenic carcinoma
  • Generally, the lymph nodes are on the same side
  • In patients with central squamous cell carcinoma or small cell carcinoma, the hilar/mediastinal mass may be the only abnormality on plain X-ray or CT
  • In patients with extrathoracic neoplasms, intrapulmonary metastases are 10 times more common than nodal metastases.
  • Most common tumors associated with nodal metastasis are:
    • Genitourinary (renal and testicular)
    • Head and neck
    • Breast
    • Melanoma
  • Isolated lymph node involvement seen in 60% cases
  • Hilar and right paratracheal are most commonly involved.
Tuberculosis: Primary tuberculosis produces an area of consolidation in one lobe with unilateral enlargement of the bronchopulmonary, paratracheal and subcranial lymph node.
  • Pleural effusion also occurs and complete calcification of the lymph node may develop as healing occurs
zoom view
Fig. 1.8: PA radiograph of chest shows superior mediastinal and bilateral adenopathy along with reticulonodular shadowing in bilateral lungs in a case of sarcoidosis
Sarcoidosis (Fig. 1.8)
  • Enlargement of the bronchopulmonary and paratracheal lymph node, which usually are bilateral
  • Enlarged lymph node in locations such as subcarinal, anterior and posterior mediastinum may be seen particularly if CT is performed.
Mediastinum (Fig. 1.9)
  • Anterior—in front of the anterior pericardium and trachea
  • Middle—within the pericardium including the trachea
  • Posterior—lies behind the posterior pericardium and trachea
zoom view
Fig. 1.9: Shows different regions in mediastinum
  • Neurogenic tumors
  • Pharyngoesophageal pouch
  • Hiatus hernia
  • Neurenteric cyst
  • Aneurysm of descending aorta
  • Sequestrated lung segment
  • Esophageal dilatation
  • Dilatation of azygous vein
  • Neurogenic tumors
  • Bochdalek's hernia
  • Paravertebral mass
  • Extramedullary hemopoiesis.
Neurenteric Cyst
  • Partial or complete persistence of the neurenteric canal or its incomplete resorption
    • Gastrointestinal reduplication
    • Enteric cysts
    • Neurenteric cysts
    • Anterior meningocele
    • Cysts of the cord
  • Associated spinal anomalies
    • Block vertebra
    • Hemivertebra
    • Butterfly vertebra
    • Spina bifida
  • Usually present in infants
  • Respiratory distress
  • Feeding difficulties
  • Cysts—appear as oval or rounded soft tissue mass in posterior mediastinum.
  • Anterior meningocele: Diagnosed by CT–myelography, prone scan
  • Esophageal duplication cyst—Barium swallow—ectopic gastric mucosa – Tc 99m positive.
Pertechnetate Scan
  • Neurenteric cyst can be diagnosed by USG/CT/MRI—usually right-sided.
Dilated Azygous Vein
  • Oval soft tissue mass in right tracheobronchial angle
  • Caused by—increased central venous pressure
    • Superior or inferior vena cava obstruction
    • Portal hypertension
    • Congenital azygous continuation of IVC
    • D/D—Enlarged azygous lymph node
    • Azygous vein—decrease in size—in erect position
    • On deep inspiration
    • During maneuver.
Esophageal Lesions
  • Pharyngoesophageal pouch or Zenker's diverticulum:
    • Round mass containing air-fluid level in the superior part of posterior mediastinum usually in the midline displaying the trachea anteriorly
  • Leiomyoma/Leiomyosarcoma—soft tissue mass
  • Lower esophageal diverticulum—rounded mass with air-fluid level behind the heart
  • Dilated esophagus—Widening of the posterior mediastinum on the right side from thoracic inlet to diaphragm with lateral displacement of azygoesophageal line. Dilated esophagus displaces the trachea anteriorly
  • Air-fluid level with non-homogeneous mottled appearance of food mixed with air diagnosis confirmed by barium swallow or CT.
Paravertebral Lesions
  • Traumatic wedge compression fracture of vertebral body with paraspinal hematoma—History of trauma
  • Pyogenic/tubercular paravertebral abscess—narrowing of disk space with involvement of vertebral endplates
  • Smooth fusiform bilateral or unilateral soft tissue mass
  • Metastasis—bone destruction with pathological fracture
  • Extramedullary hematopoiesis—lobulated mass in chronic hemolytic anemia
  • Lymphoma.
Bochdalek's Hernia
  • Developmental defect in posterolateral part of left hemidiaphragm
  • Contents of the hernial sac includes retroperitoneal fat, kidney, spleen, splenic flexure.
Large or small intestine, stomach, colon may also herniate
  • Mediastinal shift/ipsilateral hypoplastic lung
  • Thirteen pairs of ribs may be associated.
Neurogenic Tumors
  • Peripheral nerves
  1. Nerve sheath tumor
  • Neurofibroma
  • Schwannoma or neurilemmoma
  • Neurofibrosarcoma
  • Malignant schwannoma
  1. Ganglion cell tumors
  • Ganglioneuroma benign (> 10 years)
  • Ganglioneuroblastoma (5–10 years)
  • Neuroblastoma (< 5 years) (most malignant)
zoom view
Fig. 1.10: Barium study radiograph shows hiatus hernia
  1. Paraganglionic nerve tissue tumors
    ↓ (rarest)
  • Chemodectomas
  • Pheochromocytomas
    • 30% malignant
    • Childhood or young adult patient
    • Asymptomatic, back pain, spinal cord compression
    • Can be multiple in the setting of neurofibromatosis—association with lateral thoracic meningocele.
  • Radiological features—Well-defined oval soft tissue mass in paravertebral gutter
  • Nerve sheath tumors—circular, calcification—rare
  • Ganglion cell tumors—Elongated, central spicules or nodules of calcification, enlargement of intervertebral foramen, scoliosis.
Hiatus Hernia
  • Usually an incidental finding in an elderly patient
  • Often asymptomatic
  • Clinical features—dyspnea, retrosternal chest pain, epigastric discomfort, iron deficiency anemia
  • CXR—Round soft tissue mass with air or air-fluid level, behind heart, usually to the left of midline
    • Larger hernias may contain small intestine, colon, liver
    • Diagnosis—confirmed by lateral chest X-ray, barium or CT. (Fig. 1.10).
Pectus Excavatum
  • Most common congenital anomaly of sternum
  • Decreased prevertebral space—left hand deviation of heart with axial rotation
    • Increased parasternal soft tissue in right inferomedial hemithorax
    • Lateral chest X-ray and CT quantify the severity.
Table 1.7   Chest wall abnormalities
Congenital and developmental anomalies
Soft tissue tumors
  • Pectus excavatum
  • Lipomas
  • Pectus carinatum
  • Neurogenic tumors
  • Poland syndrome
  • Hemangiomas
  • Cervical rib
  • Desmoid tumors
  • Cleidocranial dysplasia
  • Lymphomas
  • Sarcomas
Inflammatory and infectious
  • Osseous tumors
  • Pyogenic
  • Osteochondroma
  • TB
  • Enchondroma
  • Actinomycosis
  • Osteoblastoma
  • Aspergillosis
  • Chondrosarcoma
  • Myeloma
  • Plasmacytoma
Non-neoplastic osseous
  • Fibrous dysplasia
  • Paget's disease
  • Giant cell tumor
  • Aneurysmal bone cyst
Pectus Carinatum
  • Protrusion of sternum anteriorly
  • May be seen in isolation or with cyanotic congenital heart disease.
Cervical Rib
  • Supernumerary rib that articulates with cervical type of transverse process.
Cleidocranial Dysostosis
  • Incomplete ossification of ribs with defective development of pubic bones, vertebral column and long bones.
Poland Syndrome
  • Partial/total absence of greater pectoral muscle and ipsilateral syndactyly
  • Atrophy of ipsilateral fifth ribs, absence of smaller pectoral muscle, aplasia of ipsilateral breast/nipple, simian crease of affected extremity.
Inflammatory and Infectious Disease
  • Primary infection rare and seen in diabetes mellitus, immunosuppression, trauma and intravenous drug abusers
  • Secondary infection due to disease processes in lung or to pleurae, empyema more common
  • May produce parenchymal infection, pleural effusion, chest wall masses, rib destruction and even cutaneous fistula, air-fluid levels may be seen in soft tissues. Patients usually have febrile cause.
Tumors of Chest Wall
  • Primarily soft tissue tumors are rare
  • In adults, most common benign soft tissue neoplasm is lipoma and most common malignant neoplasms are fibrous sarcoma and MFH
  • In children, PNET (Askian) tumor, rhabdomyosarcoma and extraosseous Ewing's sarcoma are most common malignant soft tissue tumors
  • Secondary tumors are more common in thoracic skeleton
  • Majority of osseous lesions are in ribs, large numbers are metastatic
  • Osteochondroma is most common benign tumor of cartilage bone. Most common malignant tumor is chondrosarcoma
  • Majority of lesions arising from sternum are malignant and represent chondrosarcoma most often
  • Lesions of thoracic vertebrae are invariably metastatic
  • Most common tumors to produce pattern of chest wall mass with bone destruction are metastases and small round cell tumors (multiple myeloma), Ewing's tumor and neuroblastoma. The differential diagnosis in adults is metastases versus myeloma, whereas in a child, pattern is more suggestive of Ewing's tumor or metastatic neuroblastoma.
Radiological Differentiation of Chest Wall Tumors
Imaging findings
Tumor type
  • Fat attenuation/intensity
  • Lipoma
  • Calcification
    • Skeletal
      • Amorphous
  • Fibrous dysplasia
      • Cartilaginous apical cap
  • Osteochondroma
    • Extraskeleton, punctate
  • Cavernous hemangioma
  • Cortical thinning—fluid-fluid levels
  • ABC or GCT
  • Cortical expansion, sclerotic band
  • Ossifying fibromyxoid tumor or chondromy-xoid fibroma
  • Rib erosion, well-defined contours, extraskeletal location
  • Schwannoma or non-ossifying fibroma
  • Location at costochondral junction
  • Osteochondroma
  • Location in paravertebral
  • Ganglioneuroma or regional paraganglioma
  • Location in shoulder region
  • Spindle cell lipoma
  • Fat component
  • Liposarcoma
  • Calcification
    • Skeletal
    • Rings and arcs
  • Chondrosarcoma
    • Flocculent or stippled
    • Centrally dense
  • Osteosarcoma
  • Extraskeletal
    • Heterogeneous
  • Ganglioneuroma or neuroblastoma
    • Speckled
  • Proximal type epithelioid sarcoma
  • Diffuse osteolytic changes
  • Myeloma
  • Ill-defined mass
    • Eccentric growth, in children and young adults
  • Ewing's sarcoma
    • Fluid-fluid levels and calcifications in adolescents and adults
  • Synovial sarcoma
    • Chronic lymphedema
  • Angiosarcoma
    • Infiltrative growth
  • Malignant lymphoma
  • Non-specific findings
  • LMS, RMS,
    MFH, etc.
Classification (Sargent et al)
  1. Normal.
  2. Disturbance of osteoblastic activity with decreased or deficient bone formation
    • Paralytic poliomyelitis
    • Collagen diseases
      • Scleroderma
      • Rheumatoid arthritis
      • Systemic lupus erythematosus (SLE)
    • Exostosis
    • Neurofibroma
    • Surgery
    • Osteogenesis imperfecta
    • Coarctation of aorta
    • Marfan's syndrome
    • Radiation damage
    • Quadriplegia.
  3. Disturbance of osteoclastic activity with increased bone resorption
    • Hyperparathyroidism
    • Hypovitaminosis-D.
  4. Idiopathic.
Salient Features
  • Limb deformities and muscle atrophy seen particularly involving the pectoral muscles and shoulder girdle
  • Rib notching seen in chronic cases usually involving 3rd–9th ribs
  • Unilateral hypertransradiant hemithorax
  • Scoliosis.
Rheumatoid Arthritis
  • More common in females
  • Symmetrical arthritis especially involving the MCP and PIP joints of hands and feet and wrist
  • Absence of lateral end of clavicle or pencil pointing may be seen
  • Caplan's syndrome—multiple nodules in lung
  • Subcutaneous nodules.
Systemic Sclerosis
  • Raynaud's phenomenon
  • Subcutaneous calcification—especially in the fingertips
  • Esophageal abnormalities—dilatation, atonicity, poor or absent peristalsis
  • Symmetric erosions on superior surface, predominantly along the posterior aspect of 3rd–6th ribs
  • Terminal phalanx resorption
  • Skin thickening.
Systemic Lupus Erythematosus (SLE)
  • Mostly females, butterfly rash
  • Polyarthritis: Bilateral and symmetrical involving the small joints of the hand, knee, wrist
  • MCP and PIP joint involvement—no erosions
  • Recurrent pleural effusion often with pleurisy resulting in elevation of a hemidiaphragm and plate atelectasis at base.
  • 10–20 years of age
  • Well-defined protrusion with the patent cortex and trabeculae continuous with that of parent bone. Cartilage cap
  • Most common distal femur, proximal tibia
  • Lesions arising from ribs and scapulae cause rib notching
  • Diaphyseal achalasia—multiple lesions.
  • One or more primary relatives with neurofibromas
  • Café au lait spots
  • Optic gliomas
  • Typical bone lesions—sphenoid dysplasia
    (absent greater wing or lesser wing, absent posterolateral wall of orbit)
  • Tibial pseudarthrosis
  • Rib notching, twisted ribbon ribs, splaying of ribs
  • Cerebral and cerebellar calcification, heavy calcification of choroid plexus.
Marfan's Syndrome
  • Tall stature, long slim limbs
  • Arachnodactyly
  • Joint laxity—dislocation of sternoclavicular joint and hip joint
  • Scoliosis and kyphosis
  • Pectus excavatum and carvinatum
  • Aortic sinus dilatation and aortic regurgitation.
Osteogenesis Imperfecta
  • Osteoporotic, fragile bones often with deformities secondary to fractures and mechanical stress
  • Often in infant or child with blue sclerae
  • Flattened or biconcave vertebrae
  • Wormian bones
  • Rapid fracture healing with exuberant callus
  • Wavy, thin, ribbon-like ribs with notching.
  • Subperiosteal bone erosion—particularly affecting the radial side of middle phalanx of middle finger, medial proximal tibia, lateral end of clavicle
  • Diffuse cortical damage—Pepper-pot skull
  • Brown tumors—mandible, ribs, pelvis
  • Ribs
    • Characteristically show random notching
    • Coarse sclerosis of trabecular pattern of clavicles and ribs.
  • Blalock-Taussig operation
  • Subclavian artery occlusion
  • Aortic coarctation left subclavian artery or anomalous right subclavian artery.
  • Aorta coarctation, occlusion, aortitis
    • Takayasu's disease, atheroma
    Pulmonary oligemia
    • Fallot's Tetralogy
    • Pulmonary atresia
    • Stenosis
    • SVC, IVC obstruction
Table 1.8   Types of effusion
U/L, B/L
Biochemical derangement
Cardiac failure
Hepatic failure
Nephrotic syndrome
Meigs' syndrome
U/L, B/L
U/L, B/L
Pulmonary infarction
Collagen vascular
CA bronchus
U/L, B/L
Pulmonary infarction
Bleeding disorders
Obstructive thoracic
zoom view
Fig. 1.11: PA radiograph of chest shows bilateral pleural effusion causing compression atelectasis of underlying pulmonary parenchyma (L>R)
Table 1.9   Cases of small hilum
Apparent rotation, scoliosis
Volume loss
Soft tissue
Normal or left side lobar collapse, lobectomy
Hypoplastic pulmonary artery
McLeod's syndrome
Unilateral pulmonary embolus
Cyanotic congenital heart disease
Central pulmonary embolus
  • Intercostal-pulmonary fistula
  • AV fistula
  • HPT
  • Neurogenic
  • Idiopathic.
Pleural Effusion (Fig. 1.11 and Table 1.8)
Small Hilum (Table 1.9)
  • Causes above the diaphragm
    • Phrenic nerve palsy
    • Pulmonary collapse
    • Pulmonary infarction
    • Pleural disease
    • Hemiplegia (Table 1.10)
      • Diaphragmatic cause
    • Eventration
      • Causes below the diaphragm
      • Gaseous distension of stomach/splenic flexure
      • Subphrenic inflammation of diaphragm
      • Scoliosis
      • Decubitus.
  • Poor inspiratory effort
  • Obesity
    Above the diaphragm
    • B/L basal pulmonary collapse
    • Small lungs
    Below the diaphragm
    • Ascites
    • Pregnancy
    • Pneumoperitoneum
    • Hepatosplenomegaly
    • Intra-abdominal tumor
    • B/L subphrenic abscess.
Unilaterally Elevated Diaphragm
Phrenic nerve palsy: Smooth hemidiaphragm, no movement on respiration. Paradoxical movements on sniffing.
Pleural disease: Especially old pleural disease, e.g. Hemothorax, empyema, tuberculosis and thoracotomy.
Splinting of the diaphragm: Associated with rib fracture or pleurisy due to any cause.
Hemiplegia: Associated with an upper motor neuron lesion.
Eventration: More common on the left side.
Heart is shifted to the contralateral side.
Paradoxical movements on sniffing.
Gaseous distension of stomach or splenic flexure: Only the left hemidiaphragm.
Table 1.10   Pleural lesions
Pleural calcification
Local pleural mass
Old empyema
Loculated pleural effusion
Old hemothorax
Asbestosis inhalation
Malignant mesothelioma
Pleural fibroma
Talc exposure
Subphrenic inflammatory disease: Sub-diaphragmatic abscess or infection, inflammation.
Scoliosis: Raised hemidiaphragm on the side of the concavity.
Decubitus: Raised hemidiaphragm is on the dependent side.
Bilaterally Elevated Diaphragm
  • Bilateral basal pulmonary collapse: which may be secondary to infarction or subphrenic abscess
  • Small lung due to fibrotic lung disease
  • Hepatosplenomegaly in patients of lymphoma, anemia and many infectious pathologies
  • Large intra-abdominal tumors either located in the midline or in any of the superior abdominal quadrants. Ascites in ovarian tumor can also cause this.
zoom view
Fig. 1.12: AP radiograph of chest shows honeycombing in both lungs with reduced volume of right lung
  • Spontaneous
  • Iatrogenic
  • Traumatic
  • Secondary to mediastinal emphysema
  • Secondary to lung disease
    • Emphysema
    • Honeycomb lung (Fig. 1.12)
    • Pneumonia
    • Bronchopleural fistula
  • Pneumoperitoneum.
  • Lung tear
  • Perforation of esophagus, trachea, bronchus, perforation of hollow viscera.
It may be associated with pneumothorax and subcutaneous emphysema.
  1. Lung tear: A sudden rise in the intra-alveolar pressure, often with airway narrowing, causes air to dissect through the interstitium to the hilum and then to the mediastinum.
    • Spontaneous: Following severe bout of cough or a severe strenuous exercise
    • Asthma: Usually not before two years of age
    • Diabetic ketoacidosis: Secondary to severe and protracted vomiting
    • Childbirth—due to repeated Valsalva maneuvers
    • Artificial respiration
    • Chest trauma
    • Foreign body aspiration.
  2. Perforation of esophagus, trachea or bronchus:
    • Spontaneous
    • Boerhaave's syndrome
    • Following severe and protracted vomiting
    • Trauma
    • Foreign body aspiration or inhalation
    Ruptured esophagus also produces left-sided pneumothorax, hydropneumothorax.
  3. Perforation of a hollow abdominal viscus with extension of gas via the retroperitoneum.
Right-sided Diaphragmatic Humps
At any site
  • Collapse/consolidation of the adjacent lung
  • Localized eventration
  • Loculated effusion
  • Subphrenic abscess
  • Hepatic abscess
  • Hydatid cyst
  • Hepatic metastasis.
  • Pericardial fat pad
  • Aortic aneurysm
  • Pleuropericardial cyst
  • Sequestrated segment.
  • Morgagni's hernia.
  • Bochdalek hernia.
Carcinoma: Approximately 50% of lung cancers arise centrally, i.e. in or proximal to segmental bronchi.
  • Obstruction of lumen leads to collapse and often infection
  • Peripheral tumors appear as soft tissue nodules or irregular masses and invade the adjacent tissues. Signs of collapse and consolidation may occur
  • Peripheral tumors may arise in the scar. These mass lesions may present as hilar enlargement, airway obstruction, peripheral mass lesion, mediastinal involvement, pleural and bone involvement.
    Alveolar cell CA: Arises more peripherally, probably from the type II pneumocytes. It arises within the alveoli and produces areas of consolidation.
  • Hematogenous: Breast, skeleton, urogenital
  • Lymphatic: Less common, breast
  • Endobronchial spread: Alveolar cell carcinoma
Metastasis is usually bilateral, affecting both lungs equally, with basal predominance. They are often peripheral and may be subpleural.
Cavitatory Metastases
  • Squamous cell carcinoma
  • Sarcoma.
Calcifying Metastases
  • Osteogenic sarcoma
  • Chondrosarcoma
  • Mucinous adenocarcinoma.
Endobronchial Metastases
  • Carcinoma kidney, breast
  • Large bowel.
Lymphangitis Carcinoma
Commonest sites—Lung, breast, stomach, pancreas, cervix, prostate. It is usually bilateral, but lung and breast cancers may cause unilateral lymphangitis.
Hodgkin's/Non-Hodgkin's Lymphoma
Present as nodal enlargement, which is usually bilateral, asymmetric and involves anterior mediastinal glands. These may calcify following therapy. Pulmonary infiltration may appear as areas of consolidation or areas of miliary nodules. Pleural effusion may be present in 30% of cases.
Mediastinal lymph node enlargement and pleural effusion are the commonest radiologic abnormalities.
Kaposi's sarcoma may appear as segmental or lobar consolidation. Other primary pulmonary sarcomas include fibrosarcoma, leiomyosarcoma—which appear as solitary pulmonary masses, radiographically indistinguishable from a carcinoma of the lung.
Carcinoid accounts for approximately 90% of bronchial adenomas and adenoid cystic tumors for about 10%. These appear as well-circumscribed round or ovoid solitary nodules. On CT, calcification may be seen within the tumor.
They are seen in childhood as a solitary pulmonary nodule. Thirty percent of these show calcification, often with a characteristic ‘popcorn’ appearance.
Lung Abscess
Radiographically, an abscess may or may not be surrounded by consolidation. Appearance of an air-fluid level indicates that a communication with the airway has developed. It shows thick irregular wall, which shows postcontrast enhancement.
It is the irreversible dilatation of one or more bronchi and is usually the result of severe, recurrent and chronic infection. It is frequently basal but in tuberculosis and cystic fibrosis, it usually involves the upper zone. Dilated bronchi produce tramline shadows or ring shadows, and dilated, fluid-filled bronchi may cause ‘gloved friger’ shadows.
During an attack, the chest X-ray may show signs of hyperinflation, with the depression of the diaphragm and expansion of the retrosternal air space. The peripheral pulmonary vessels appear normal, but if the central pulmonary arteries are enlarged, the irreversible pulmonary arterial hypertension is probably present.
Chronic Bronchitis
Fifty percent of these patients may have normal chest X-ray. In patients with a plain film abnormality, the signs are due to emphysema, superimposed infection or possibly bronchiectasis. ‘Dirty chest’ appearance is seen.
Emphysema (Fig. 1.13)
With emphysema, air trapping is present, the lung volumes increase, the diaphragm becomes flattened, and the retrosternal air space increases. The number and size of the peripheral vessels decrease. Central pulmonary arteries may enlarge suggestive of cor pulmonale.
It results due to infection (often in childhood) or due to inhalation of toxic fumers, drug therapy and rheumatoid disease. Radiologically, the appearances are most frequently of hyperinflation of lungs and perihilar prominence and indistinctness.
Unilateral Hilar Enlargement (Fig. 1.11)
Carcinoma bronchus: The hilar enlargement may be due to the tumor itself or due to the involved lymph nodes.
: Unilateral is very unusual
: Anterior mediastinal nodes are also involved
: Due to the nodal enlargement
Poststenotic dilatation of the pulmonary artery
: Usually on the left side
Table 1.11   Unilateral
Egg shell calcifcation
Air broncho-gram
Lymph Node
Pulmonary Artery
Poststenotic dilatation
Pulmonary embolus
Mediastinal mass—superimposed on a hilum
Perihilar pneumonia
Table 1.12   Bilateral
Lymphangitis carcinomatosis
Primary TB
Pulmonary arterial hypertension
Extrinsic allergic alveolitis
Pulmonary embolus
: Peripheral oligemia is characteristic
: In chronic pulmonary arterial hypertension. Calcification may also be present
Mediastinal mass
: Middle mediastinum masses may superimpose.
Perihilar pneumonia, ill-defined borders with presence of air bronchogram.
Bilateral Hilar Enlargement
: Symmetrical, lobulated. Associated bronchotracheal, tracheobronchial and paratracheal lymphadenopathy
: Asymmetrical, but multiple sites
zoom view
Fig. 1.13: PA radiograph of chest shows bilateral pulmonary emphysema
zoom view
Fig. 1.14: PA radiograph of chest shows left hilar mass
: Viral, mainly in children
TB-B/L is rare
Histoplasmosis pulmonary nodules (multiple) accompany
Pulmonary arterial
: Bilaterally is rare
Peripheral oligemia is characteristic
: Symmetrical
Pinpoint multiple pulmonary nodules are present
Table 1.13   Differential diagnosis of apical shadows
U/L, B/L
Ellis curve
Pleural outline seen
Rib destruction
Pleural caps
Pleural fluid
U/L or B/L
Pancoast's tumor
Infections – TB
U/L or B/L
Soft tissue
Intrapulmonary (Figs 1.15 and 1.16)
Granuloma, infection
Chronic abscess
Alveolar microlithiasis
Lymph Nodes
TB, histoplasmosis, sarcoidosis, silicosis.
TB, asbestosis, talcosis
Hemothorax, empyema
zoom view
Fig. 1.15: PA radiograph of chest shows multifocal pulmonary parenchymal, bilateral axillary and right cervical nodal calcifications associated with fibrotic changes in a case of healed Koch's chest
zoom view
Fig. 1.16: PA radiograph of chest shows multifocal pulmonary parenchymal and hilar calcifications associated with fibrotic changes in a case of healed Koch's chest
Pulmonary Artery
Chest Wall
Costal cartilage
Bone tumor, callus
Soft tissues.
Bronchopleural fistula
Pharyngeal pouch, diverticulae
Obstruction – tumor, achalasia esophagectomy
Perforation – esophageal
Diagnostic, trauma
Chest wall
Hernia, eventration, rupture
Crescent Sign
  • Fungal ball
  • Blood clot in tubercular cavity
  • Bronchial adenoma, carcinoma
  • Hamartoma
  • Hydatid cyst
  • Pulmonary infarct.
  • Staphylococcus
  • Klebsiella
  • Tuberculosis
  • Histoplasmosis
  • Amebic
  • Hydatid
  • Fungal.
  • Primary
  • Secondary
  • Lymphoma.
  • Blood borne
  • Aspiration
  • Pulmonary infarct
  • Pulmonary hematoma
  • Pneumoconiosis.
Collagen Diseases
  • Rheumatoid nodules
  • Wegener's granulomatosis.
  • Sequestrated segment
  • Bronchogenic cyst
  • Congenital cystic adenomatoid malformation
  • Sarcoidosis
  • Bullae, blebs
  • Pneumatocele
  • Traumatic lung cyst.
  1. Mycetoma—Aspergilloma
  2. Tissue fragment from carcinoma
  3. Necrotic lung within abscess
  4. Disintegrating hydatid cyst
  5. Intra-cavitatory blood clot.
Table 1.14   Differential diagnosis of mass within cavity
Thick, irregular walled cavity
Adjacent lung parenchymal reaction
Clinical history
of infection
of wt. loss
Contrast enh-ancement in CT of mass
+/− if chronic.
  • Malignant
    • Primary
    • Secondary
    • Lymphoma
  • Infections
    • Tuberculosis
    • Staphylococcus
    • Klebsiella
    • Amebic
    • Hydatid
    • Fungal
  • Abscess
    • Aspiration
    • Blood borne
  • Pulmonary infarct
  • Hematoma
  • Pneumoconiosis
    • Pulmonary massive fibrosis
    • Rheumatoid nodular
    • Collagen diseases
    • Wegener's granulomatosis
  • Developmental
    • Sequestration
    • Bronchogenic cyst
    • Congenital cystic adenomatoid malformation
  • Sarcoidosis
  • Bullae, blebs
  • Traumatic lung cyst
  • Pneumatocele.
Very frequently cavity nodules turn out to be malignant.
Obstruction of an artery
(Infection of a nodule)
  • In 2–10%, especially peripheral upper lobe involvement
  • Most cavities are thick-walled, irregular inner surface
  • Thickness > 15 mm—85–90% malignant
  • Cavitation—centric or eccentric
  • Multiple cavitations
  • More common in squamous cell carcinoma and then may be thin-walled.
  • More common in upper lobe, may involve few nodules
  • Thin or thick-walled
  • Seen especially in squamous cell carcinoma—head and neck (uncommon in adenocarcinoma—especially colon)
  • Sarcoma—osteosarcoma.
Hodgkin's Disease
  • Thick or thin-walled
  • Typically in an area of infiltration
  • Hilar or mediastinal LN.
  • Thick-walled and smooth, sometimes fluid level
  • Mainly affects upper lobes and apical segment of lower lobe
  • Usually surrounded by consolidation and fibrosis
  • Typically there is large cavity surrounded by smaller satellite cavities
  • Cavity walls are lined by tuberculous granulation tissue
  • Cavities traversed by fibrotic remnants of bronchi and vessels
  • Rasmussen aneurysm.
Staphylococcus aureus
  • Mostly children, multiple
  • Thick-walled cavities with a ragged inner lining
  • No lobar predilection
  • Associated with effusion and empyema.
Hydatid Cysts
  • Complicated hydatid cyst
  • Rupture into a bronchus-air crescent sign/air cap
  • Water lily sign.
  • Any pulmonary cavity—TB, histoplasmosis, sarcoidosis
  • Forms a ball which changes position, ball is seen to be mobile
  • Almost always pleural thickening related to mycetoma
  • Vascular granular tissue-bleeding may occur.
Abscess (Aspiration)
  • Multiple or single
  • Usually thick-walled
  • Following aspiration
  • Posterior segment or apical segment-UL
  • In sitting-right lower lobe.
Pulmonary Infarct
(Infection—may be)
  1. Septic embolus
Secondary to:
  1. Initially sterile, infarct, infection
Tertiary to:
  1. As aseptic cavitating infarct infected
    • Aseptic cavitation is usually solitary and arises in a large area of consolidation after about two weeks.
    • Cavity has scalloped inner margins and cross cavity band shadows/effusion.
Cystic Bronchiectasis (Fig. 1.17)
  • Thin-walled lower lobes
  • Air-fluid levels, peribronchial thickening and retained secretions
  • Crowded vessels and retained secretions.
Sequestered Lung
  • Thin- or thick-walled
  • 66% in left lower lobe, 33% in right lower lobe
  • Air-fluid level, surrounding pneumonia.
Wegener's Granulomatosis
  • Bilateral and widely spread
  • Nodules, cavitation in some nodules (1/3)
    zoom view
    Fig. 1.17: PA radiograph of chest shows bilateral perihilar cystic bronchiectasis
  • Cavities are thick-walled, shaggy/irregular lining
  • Become thinner with time
  • After-therapy may disappear.
Rheumatoid Nodules
  • Thick-walled with a smooth inner lining and well-defined
  • Lower lobes and peripherally
  • Become thinner with time.
Progressive Massive Fibrosis
  • Predominantly in mid and upper zone
  • Begin peripherally and move centrally
  • Nodule formation which cavitates into thick and irregular walled cavities in a background nodularity of pneumoconiosis.
  • In early disease, necrosis of coalescent granuloma and check valve mechanism beyond partial obstruction
  • Thin-walled cavities
  • B/L hilar lymph nodes.
Infected Emphysematous Bullae
  • Thin-walled, air-fluid level
  • Usually seen in emphysema, particularly paraseptal and scar associated
  • Apical asymptomatic and those associated with scarring (throughout the lungs—COPD)
  • Associated changes of inflammation in surrounding lung.
  • Air-fluid level—communication with bronchus.
Traumatic Lung Cyst
  • Single or multiple
  • Peripheral and thin-walled
  • Uni- or multilocular
  • Within hours of injury.
Bronchogenic Cyst
  • Medial 1/3 of lower lobes
  • If ruptures into a bronchus, thin-walled, air-fluid level and surrounding pneumonia.
Cystic Adenomatoid Malformation
  • Causes neonatal respiratory distress
  • Cavities of various shapes and sizes scattered in an area of opaque lung with well-defined margins.
Multiple Lucent Lung Lesions
  • Bacterial pneumonia
  • Granulomatous infection (Fig. 1.18)
  • Parasites.
zoom view
Fig. 1.18: PA radiograph of chest shows right upper lobe cavitation in a patient of Koch's chest
  • Wegener granulomatosis
  • Rheumatoid arthritis
  • Thromboembolic or septic infarct
    • Cystic fibrosis
    • Tuberculosis
    • ABPA
    • Recurrent bacterial pneumonia.
  • Cystic bronchiectasis
  • Pneumatocele
  • Congenital lesions—multiple bronchogenic cysts
    • Intralobar sequestration
    • CCAM Type I
    • Diaphragmatic hernia
  • Centrilobar emphysema
  • Honeycomb lung disease.
Differential Features are same as Localized Lucent Defects (Table 1.15)
Thick-walled > 1 cm
Clear, smooth
Irregular, ragged wall
Well-defined wall
Adjacent lung parenchyma
May show reactive changes
Air-fluid level +/−
Alveolar cell carcinoma
Connective tissue tumor
Round pneumonia
Pulmonary infarct
Pulmonary hematoma
Collagen disease
Rheumatoid arthritis
Wegener's granulomatosis
Bronchogenic cyst
Sequestration segment
Congenital bronchial atresia
Impacted mucus
Intraparenchymal lymph node
Loculated fluid
Skin and chest wall lesions
Table 1.15   Localized lucent defect
Air-fluid level
Specific points
Any zone
Multi cystic with areas of break-down
Fibrosis and cavitating
Less likely to be apical
Fungal ball
Upper zone
B/L hilar and R para-tracheal LNs
Cystic bron-chiectasis
Lower lobes
Air-fluid level
In area of infection
Staph. infection Sequelae
Previous pneumonia/ posttraumatic hematoma
Intralobar sequestration
Lower lobes
Vascular drainage is altered
Honey-combing Lung CCAM
Any zone
Acq./End state disease Cong.
Cartilage Deve-lopment is defective
Definition (Fig. 1.19)
Single, round intraparenchymal opacity, at least moderately well-marginated and not greater than 3 cm in maximum diameter.
  • Benign—Hamartoma, inflammatory pseudotumor (Table 1.16)
  • Malignant—Bronchogenic carcinoma, carcinoid tumor, metastasis (Figs 1.20 and 1.21).
  • Granuloma—Tuberculoma
  • Fungal—Histoplasmoma
  • Abscess
  • Round pneumonia
  • Parasites—Echinococcus.
  • Connective tissue—Wegener's granulomatosis
    • Rheumatoid nodule
    • Sarcoidosis (rare).
  • Arteriovenous malformation
  • Hematoma
  • Pulmonary infarct
  • Pulmonary artery aneurysm.
  • Congenital lesion—Bronchogenic cyst
  • Mucocele
    zoom view
    Fig. 1.19: PA radiograph of chest shows solitary pulmonary nodule in right upper lobe peripherally
    zoom view
    Fig. 1.20: PA radiograph of chest shows bronchogenic carcinoma in right upper lobe with pulmonary metastases in left lower lobe
    zoom view
    Fig. 1.21: PA radiograph of chest shows multifocal pulmonary metastases from breast carcinoma
  • Infected bulla
  • Pseudonodules
  • ECG pads
  • Cutaneous lesions
  • Mole
  • Nipple shadow
  • Hemangiomas
  • Neurofibromas
  • Lipomas.
Characteristics of SPN
  1. Size
    • No size criteria that clearly distinguishes benign from malignant SPN
    • 80% of benign SPN <2 cm in diameter
    • 15% of malignant SPN <1 cm in diameter
    • 42% of malignant SPN <2 cm in diameter
  2. Growth
    • Benign lesions—<30 days or <450 days (doubling time) SPN with doubling time between 30 and 450 days require further evaluation
    • Doubling time for spherical lesions is defined as 25% increase in diameter.
  3. Calcification
    • Approximately 1/3rd of non-calcified SPNs have calcification on CT
    • Complete/central/laminated: Granulomas
      Popcorn: Hamartoma
      Amorphous/Eccentric calcifications: Malignancy.
  4. Fat
    Fat within a smooth/lobulated SPN is suspected benignity of hamartoma—50% show presence of fat.
  5. Cavitation
    Cavities with greatest wall thickness <5 mm are benign >15 mm are malignant.
  6. Air bronchogram/bubbly lucencies
    • Presence of air bronchogram within SPN is suggestive of adenocarcinoma, particularly bronchoalveolar cell carcinoma.
    • Other causes – Lymphoma, organizing pneumonia, pulmonary infarcts and mass-like sarcoidosis.
  7. Margins
    • Smooth, well-defined margins symptoms of benign nodule although 21% of malignant nodules smooth margin
    • Lobulated/ill-defined/spiculated symptoms of malignant nodule 25% of benign nodules may have undefined margins
    • Presence of a small satellite nodule surrounding the periphery of a smooth SPN is symptom of granulomatosis infection.
CT Nodule Enhancement
  • Enhancement <15 HU symptom of benign nodule
  • False +ve: Central necrosis, mucin producing malignant neoplasm
  • Enhancement > 15 HU—Non-specific.
Pulmonary Hamartomas
  • These consist of masses of cartilage with clefts lined by bronchial epithelium which may contain large calcification (popcorn) of fat; Age group: 45–50 years
  • Triad: Pulmonary chondromas
    (Carney's triad): Gastric epitheloid leiomyosarcomas
  • Functioning extra adrenal paragangliomas
  • 90% peripheral and 10% within a major bronchus
  • Spherical lobulated SPN with popcorn calcification, size <4 cm, fat density positive.
Inflammatory Pseudotumor (Plasma Cell Granuloma)
  • Caused histology by mixture of fibroblasts, histiocytes, lymphocytes and plasma cells
  • Age range is wide and includes children
  • SPN (2–5 cm) or as an area of consolidation, calcification is occasionally present.
Endobronchial tumor can cause obstructive pneumonitis.
Bronchial Carcinoid
Bronchial carcinoids can invade locally, may metastasize to hilar and mediastinal lymph nodes as well as to brain, liver and bone.
  • Age: Age range is wide; Peak—5 decades.
  • Clinical features—Wheeze, Cushing's syndrome (ectopic ACTH secretion), Carcinoid syndrome
  • Hilar/parahilar mass
  • 80–90% Central (endobronchial)
  • 10–20% Peripheral with features of bronchial obstruction, pneumonia, Calcification +/−
  • Spherical/lobular SPN (2–4 cm) smooth well-defined margin calcification +/−.
Bronchial Carcinoma (Fig. 1.22)
  • Squamous cell carainoma (30–50%)
  • Adeno carainoma (30–50%)
  • Undefined small cell carainoma (20–30%)
  • Large cell carcinoma (10–15%)
  • Peak incidence: 50 to 60 years
  • Radiological features: Size > 2cm
    • Undefined margins
    • Umbilicated/notched margin
    • Corona radiata/speculations (+)
    • Pleural tail sign (+)
    • Doubling time between 30 and 450 days
    • Lesion crosses fissure
    • Cavitation: (>15 mm thick wall)
    • Calcification rare if present—eccentric
  • Associated findings—Hilar/mediastinal lymph nodes, bone mets, pleural effusion, visceral mets (+)
  • Bronchoalveolar Carcinoma: Air bronchogram/bobby lucencies
    • Grows slowly
    • Cavitation is unusual.
Pulmonary metastasis is usually from breast, GI tract, kidney, testes, head and neck tumors or from a bone and soft tissue sarcomas.
  • Site: Usually in the outer portions of lung
  • Radiological features (R/f)—solitary/multiple
  • Spherical well-defined, occasionally irregular edge
  • Calcification—unusual except metastases from osteosarcoma, chondrosarcoma
    zoom view
    Fig. 1.22: PA radiograph of chest shows bronchogenic carcinoma in right upper lobe
  • Rate of growth: Variable—explosive in choriocarcinoma and osteosarcoma
  • Cavitation—unusual (squamous cell carcinoma +).
  • Occurs in the setting of primary or postprimary tuberculosis and is considered to represent localized parenchymal diseases that alternatively activate and heal
    Nodule is 10–15 mm in diameter
    Situated most commonly in the right upper zone
    Single or multiple (confined to a single segment)
    Margins well-defined
    Satellite lesions (+)
    Calcification frequent
    Cavitation +/−.
Hydatid Cyst
Caused by tapeworm (E granulosus or E alveolaris)
  • Humans are accidental host
  • Infection occurs by ingestion of ova by fomites/contaminated water.
Radiological features (R/f) Unruptured cyst: Homogenous spherical/ oval, well-defined lesion. Size 1 to 10 cm occurs particularly in middle zone/lower zone.
Ruptured cyst: Usually associated with secondary infection
  1. Meniscus sign—Pericyst—ruptures ectocyst and endocyst intact appearance is that of an intracavitary body.
  2. Disruption of inner layers:
    1. Air-fluid level
    2. Floating membranes (water lily, camalote sign)
    3. Double wall appearance
    4. Dry cyst with crumpled membranes lying at its bottom (rising sun, serpent sign)
    5. Cyst with all its contents expectorated (empty cyst sign).
Caused by histoplasma capsulatum which is a fungus found in moist soil and in bird or bat excreta.
Histoplasma represents a small necrotic focus of infection surrounded by a massive fibrous capsule consisting of concentric lamination, some or all of which may calcify.
  • Sharply-defined nodular shadow
  • <3 cm in diameter
  • Most common site is in the lower lobe
  • Satellite lesions (+)
  • Calcification (+) central/eccentric
  • Target lesion is pathognomonic—Homogeneous density with central punctate deposit of calcium
  • Associated findings – Calcified hilar/mediastinal lymph nodes.
Round pneumonias are usually pneumococcal which are usually seen in children, air bronchogram.
Lung Abscess
Cavitation secondary to necrosis is seen in:
Bacterial pneumoniasStaphylococcus aureus
  • Gram-negative bacteria—Klebsiella pneumoniae, Proteus pseudomonas
  • Anaerobes
  • Amebic and fungal infections.
Cavitary Lesion with Adjacent Consolidation
Size—2 to 12 cm
Wall thickness < 15 mm
Inner aspect of cavity is smooth.
Wegener's Granulomatosis
  • Necrotizing granulomatous vasculitis
  • Lungs involved in 95% cases and late renal involvement is seen in 85% cases
  • Men>Women
  • Single/multiple nodules
  • Size = 1 cm to several cm
  • Well-defined margins
  • Wax and wane
  • Frequently cavitate
  • Associated findings—Granulomas in upper respiratory tract and glomerulonephritis.
Rheumatoid Nodules
Pleuropulmonary is seen in 5 to 54% cases of rheumatoid arthritis.
  • Pulmonary, necrobiotic nodules are uncommon features of rheumatoid arthritis
  • Associated with subcutaneous nodules
  • Single/multiple
  • Variable in size
  • Wax and wane in size
  • Cavitation (+) / (−) more common in lower lobe and in periphery.
  • Similar nodule may be seen in patients of rheumatoid arthritis who have been exposed to silica. Known as Caplan's syndrome.
Pulmonary A-V Fistula
Congenital—50% have hereditary hemorrhagic telangiectasia
  • (Osler-Weber-Rendu disease)
  • Acquired—Liver diseases (cirrhosis), schistosomiasis and metastatic thyroid cancer
  • Round/lobulated nodule
  • Prominent adjacent vascular shadow
  • Most common site—Lower lobe
  • Variation in size with Valsalva (size)
  • CT and pulmonary angiography shows the feeding artery and vein and vascular nature of nodule.
Pulmonary Artery Aneurysm
Most pulmonary artery aneurysms are acquired as a result of septic embolization or an extension from a pulmonary parenchymal calcification.
  • Peripheral aneurysms may mimic SPN pulsations of mass seen on fluoroscopy
  • Confirmation done by CT or pulmonary angiography.
Pulmonary Hematoma
History of (H/o) trauma (+); usually appears following resolution of contusion.
  • Peripheral in location
  • Smooth and well-defined
  • Slow resolution over several weeks
  • A pocket of air or fluid level (+).
Pulmonary Infarct
  • Becomes visible 12–24 hours after embolic episode
  • Lesions are more frequent in the lower lobe
  • Hump-shaped opacity with its base applied to the pleural surface because of partial collapse, hemorrhagic congestion
  • Cavitation is rare
  • Matched defect is seen on ventricular perfusion scan
  • Associated pleural effusion (+).
Bronchogenic Cyst
  • Peak incidence is in 2nd and 3rd decades
  • 2/3rd are intrapulmonary and occur in the medial 1/3rd of the lower pulmonary region
  • Round to oval
  • Smooth-walled and well-defined
  • CT shows thin-walled water density cyst.
  1. Congenital absence or hypoplasia of a pulmonary artery
  2. McLeod's syndrome
  3. Thromboembolism
  4. Unilateral emphysema
  5. Lobectomy
  6. Pleural disease.
Localized Air Space Disease
  • Pneumonia
  • Infarction
  • Contusion
  • Edema
  • Radiation
  • Alveolar cell carcinoma.
  • Differential features are discussed in alveolar shadowing.
Unilateral Pulmonary Edema
  • Pulmonary edema on the same side as a pre-existing abnormality
  • Prolonged lateral decubitus
    Table 1.16   Clinical and Radiographic Criteria for Differentiating Benign and Malignant SPN
    • Age
    <40 years except hamartomas
    >45 years
    • Sex
    • History
    • High incidence of granuloma in area
    • Primary lesion else-where
    • Exposure to tuberculosis
    • History of smoking
    • Skin test
    Positive with specific infectious organism
    Small (<2 cm)
    Large (>2 cm)
    No predilection except for tuberculosis
    Predominantly on upper lobes except for lung metastases
    Definition and contour
    Well-defined and smooth
    III-defined, lobulated umbilicated
    Central, laminated popcorn, complete
    Eccentric (very rare)
    Satellite lesion
    More common
    Less common
    Doubling time
    <30 to >450 days
    30 to 450 days
    Presence of fat
    (+) Symptom of hamartoma
  • Unilateral aspiration
  • Pulmonary contusion
  • Rapid thoracocentesis of air or fluid
  • Bronchial obstruction
  • Clinical history is most important in the differential diagnosis of all the above entities.
Bronchial obstruction:
  • Respiratory distress +/−
  • Examination of (E/o) occlusion: It is seen in the form of luminal obstruction, atelectasis, fissural displacement.
Alveolar Shadowing
Pulmonary edema
  • Non-cardiac
    • Hypoproteinemia
    • Fluid overload
    • Drowning
    • Aspiration
    • Inhalation
    • ARDS, uremia
    • Infection
  • At birth
  • Aspiration
  • Hyaline membrane disease (Fig. 1.23)
  • Alveolar
  • Blood pulmonary hemorrhage
  • In hematoma
  • Goodpasture's syndrome
  • Pulmonary infarction.
  • Tumors
  • Alveolar cell carcinoma
    Table 1.17   Causes of pulmonary edema
    Congenital absence or hypoplasia of a pulmonary artery
    Macleod's syndrome
    Unilateral emphysema
    Pleural disease
    Lack of soft tissue outline
    Prominent hilum
    Subpleural consolidation
    Elevated diaphragm
    Pleural reaction
    Mediastinal shift
    Linear outline of pleura
    Air broncho-gram
    Rapid Resolution
    Reticulono-dular pattern
    Peripheral, central
    Hyaline Membrane disease
    Whole lung
    Usually presents with unusual features
    Right UL in Erect Right LL in Supine
    During resolution
    White out lung
    Hemor-rhage/ contusion
    Clinical h/o
    Alveolar cell carci-noma
    Nonresolving Pneumonia
    Clinical h/o
    Air broncho-gram
    Embolism/ infarct
    1–2 day post-trauma resolves in 1–4 weeks
    Löffler's syndrome
    Follow the exposure history
    + in acute-in chronic
    Usually from chronic CA
  • Lymphoma
  • Alveolar proteinosis
    • Microlithiasis
  • Radiation pneumonitis
  • Sarcoidosis
  • Eosinophilic lung.
  • 4–10 mm diameter
  • Ill-defined margins
  • Coalescence
  • Non-segmental.
Air Bronchogram
  1. Consolidation pneumonic
  2. Pulmonary edema
  3. Hyaline membrane disease.
  1. Lymphoma
  2. Sarcoidosis
  3. Alveolar proteinosis
  4. Alveolar cell carcinoma
  5. Adult respiratory distress syndrome.
  • Asymmetrical, irregular
  • Thickening
  • Calcification +/−
  • U/L
zoom view
Fig. 1.23: Anteroposterior radiograph of chest in neonate shows hyaline membrane disease
  • Rib resection +/−
  • Thoracoplasty asymmetrical bony contour
  • H/o present.
Pulmonary Agenesis
  • Congenital anomaly
  • Respiratory distress +
  • Status of diaphragm.
Differential Diagnosis (D/D) Diaphragmatic Hernia
  • Scaphoid Abdomen
Bowel loops with air +/−
Opaque thorax
A few lucencies +
Any zone
Any zone
Pleural effusion
Hilar enlargement
Silhouette with cardiac
Crazy pavement pattern
White out lung
Vascular markings visualized
Air bronchogram
Confined to one segment
Air alveologram
Vessels not seen
Crowding of fissure and ribs
Hilar and diaphragmatic displacement.
Examination of (E/o) volume loss +.
Cardiac contour conforming of uni/multi-chamber enlargement.
D/D Miliary Shadowing
Disseminated pulmonary opacities
  1. Acinar
  2. Interstitial
Acinar—poorly-defined, round, parenchymal opacities
  • 4–8 mm in diameter
  • Represent an anatomical acinus filled with fluid.
Interstitial (Fig. 1.24)
Pulmonary interstitium is a network of connective tissue fibers that supports the lung. It includes alveolar walls, interlobular septa and peribronchovascular interstitium.
zoom view
Fig. 1.24: Posteroanterior radiograph of chest shows bilateral interstitial pulmonary disease
Interstitial nodules may take various patterns.
  • Linear and septal lines
  • Miliary shadows
  • Reticulonodular shadows
  • Honeycomb shadows
  • Peribronchial cuffing and ground glass pattern
  1. Fluffy, ill-defined
  1. 4–8 mm
2–4 mm
  1. Coalescent
  1. Segmental/lobar
  1. Air bronchogram
Usually 1 week
  1. Time from onset of nodules is less
Usually more than one week
  1. Higher density
Lower density
Miliary Shadowing
It is the presence of small, discrete, rounded pulmonary nodules of almost similar size measuring 2–4 mm in the interstitium.
  1. Infectious diseases:
    1. Tuberculosis
    2. Fungal infections—Histoplasmosis, coccidioidomycosis, blastomycosis
    3. Chicken pox.
  2. Inhalational diseases:
    1. Silicosis
    2. Barytosis
    3. Stannosis
    4. Coal miner's pneumoconiosis
    5. Berryliosis
  3. Granulomatous diseases:
    1. Sarcoidosis
    2. Histiocytosis-X103
  4. Metastases
  5. Secondary hyperparathyroidism
  6. Oil embolism
  7. Alveolar microlithiasis
  8. Hemosiderosis
  9. Bronchiolitis obliterans.
Miliary Tuberculosis (Fig. 1.25)
  • Due to hematogenous spread of infection
  • May be seen in both primary and postprimary disease
  • Small discrete nodules 1–2 mm in diameter, evenly distributed throughout both lungs
  • These are of soft tissue density and are well-defined
  • Other tubercular manifestations as consolidation, pleural effusion, and lymphadenopathy may be present.
  • Due to infection with histoplasma capsulatum
  • Infection is usually subclinical and heals spontaneously leaving small calcified nodules or calcified mediastinal nodes
  • Infection in immunocompromised patient may produce multiple nodules scattered throughout the lung, resulting in miliary shadowing
  • Hilar nodes enlargement is common
  • Consolidation, fibrosis and cavitation may occur.
  • Multiple nodular shadows 2–5 mm in diameter
  • Affects mainly mid and upper zones, relatively sparing the bases
  • Hilar adenopathy which may calcify, fibrosis, cavitation may occur.
zoom view
Fig. 1.25: Posteroanterior radiograph of chest shows miliary tuberculosis
Coal Miner's Pneumoconiosis
  • Small, faint nodules 1–5 mm in diameter appear in mid zone spreading to whole lung
  • Progressive massive fibrosis—mid and upper zones—in complicated cases
  • Emphysematous bullae may appear.
  • Multisystem granulomatous disorder affecting young adults
  • 75–90% patients show small, rounded or irregular nodules 2–4 mm in diameter, bilaterally symmetrical with upper and mid zone preponderance
  • Bilateral symmetrical lymphadenopathy, hilar and paratracheal
  • Air trapping, pleural thickening and effusion may be positive.
Histiocytosis X
  • Granulomatous disorder affecting young or middle-aged adults
  • Pulmonary involvement is bilaterally symmetrical
  • Chest X-ray shows diffuse nodular pattern in upper and mid zones, 1–5 mm in size. Progress of disease leads to ring shadows, honeycombing and linear shadows.
Miliary Metastasis
  • Rare cause of miliary shadowing
  • Primary tumors most likely to provide miliary nodulation are thyroid, renal carcinoma, bone sarcomas and choriocarcinomas.
In patients with heart disease which elevates left atrial pressure, e.g. in mitral stenosis, there is permanent miliary stippling due to focal nature of bleeding.
Alveolar Microlithiasis
  • Multiple fine sand-like calculi in the alveoli
  • Produce widespread dense opacities on chest X-ray
  • Clinically there is relative lack of symptoms.
  • Soft tissue densities
  • Miliary tuberculosis
  • Fungal disease
  • Pneumoconiosis
  • Sarcoidosis
  • Extrinsic allergic alveolitis
  • Fibrosing alveolitis
Greater than Soft Tissue Density
  • Hemosiderosis
  • Silicosis
  • Siderosis
  • Stannosis
  • Barylosis.
These are diseases caused by inhalation of inorganic dusts. The diagnosis depends on a history of exposure to the dust and an abnormal chest radiograph and respiratory function tests.
  • Gold-mining, sand-blasting, foundry, ceramic and pottery workers
  • Multiple, nodular shadows 2–5 mm in diameter mid and upper zones
  • Linear lines and septal lines may also be seen.
Coal Workers
  • Pneumoconiosis
  • Small, faint, indistinct nodules 1–5 mm in diameter appear in the mid zones
  • Coalescence of these nodules is common
  • Develop bilaterally
  • Fibrotic masses may calcify.
Asbestosis (Fig. 1.26)
Asbestosis mining and processing.
In construction and demolition workers, ship-building.
  • Lower zones nodules
  • Pleural plaque, calcification, diffuse thickening and effusion—mid zone, bilaterally
  • Pulmonary fibrosis is marked107
  • Initially reticulonodular pattern results—which with progression becomes coarser and there is loss of clarity of the diaphragm and heart.
In the acute stage, produces non-cardiogenic pulmonary edema, while in the chronic stage, produces widespread non-cavitating granulomas.
  1. Post-lymphogram
  2. Silicosis
  3. Stannosis
  4. Baryltosis
  5. Alveolar microlithiasis.
zoom view
Fig. 1.26: Posteroanterior radiograph of chest shows calcified pleural plaque in left hemithorax
Table 1.18   Multiple Opacities (2–5 mm)
Remaining discrete
Mid zone
Tending to confluence and varying rapidly
Multifocal pneumonia
Pulmonary edema
Extrinsic allergic
Fat emboli
Table 1.19   Spectrum Multiple Pinpoint Opacities
At the termination of the thoracic duct
In gold miners
Inhalation of tin oxide
Near thoracic duct
Bases and apices spared
Kerley lines
Inhalation of barytes
Negative shadows
Septal Lines
  • Pulmonary edema
  • Mitral valve disease
  • Pneumoconiosis
  • Lymphangitis carcinomatosa109
    zoom view
    Fig. 1.27: Posteroanterior radiograph of chest shows opaque right hemithorax with fairly preserved hemithoracic volume
  • Sarcoidosis
  • Infection
  • Lymphoma.
Causes (Figs 1.27 and 1.28)
Rotation, scoliosis
Hydrothorax, lung effusion thickening, mesothelioma
Pneumonectomy, thoracoplasty
Pulmonary agenesis
Gross cardiomegaly, tumors
Collapse, consolidation, fibrosis
zoom view
Fig. 1.28: Posteroa nterior radiograph of chest shows opacities in left hemithorax with loss of volume with subsegmental pneumonitis in right middle zone in a case of Koch's chest
Diaphragmatic Hernia
  • Lucency on
  • Concave side
  • Rotated side
Clavicular asymmetry
  • Blunted cardiophrenic angle
  • Fluid along the lateral chest wall
  • Silhouette with cardiac and diaphragm
  • Changes with change of posture
  • Thickening
    • Does not follow
      Ellis curve
  • Technical
Rotation, scoliosis
  • Pleural
    • Pleural thickening
    • Mesothelioma
Pleural effusion
  • Surgical
    • Thoracoplasty
  • Congenital
Pulmonary agenesis
  • Mediastinal
Gross cardiomegaly, tumors
  • Pulmonary
Collapse, consolidation, fibrosis
  • Diaphragmatic hernia
  • In well-centered film, medial ends of clavicle are equidistant from spinous process of T4/5 level
  • Lung nearest to the film, less translucent.
Pleural Effusion
  • A massive effusion may cause complete radiopacity of a hemithorax
  • Mediastinal shift to contralateral side
  • Inversion of diaphragm
  • If effusion without mediastinal shift, collapse of underlying lung.
Exclude Carcinoma Bronchus
  • Ultrasound reveals fluid in pleural cavity. In AP-CXR—with patient supine a small effusion gravitates posteriorly—generalized increased density with apical cap
  • Erect or decubitus film confirms the diagnosis
  • Pulmonary agenesis/aplasia/hypoplasia.
  • Complete absence of the lobe as well as its bronchus
  • Absent vascular supply.
  • No lung tissue
  • Rudimentary bronchus.
  • Bronchi and alveoli are present, but the lobe is under-developed
  • More common on right side
  • Mediastinal shifts present. Absence of a lobe is more common than absence of whole lung
  • Loss of silhouette on the right side of the heart and ascending aorta due to deposition of extrapleural alveolar tissue
  • If whole lung absent—completely opaque hemithorax with mediastinal shift and diaphragmatic shift
  • Unlike acquired pneumonectomy, gross loss of lung volume, external diameter is not considerably less than normal side in congenital absence
  • Bronchography—diagnostic
  • Scintigraphy—absent ventilation and perfusion on the affected site
  • Angiography—absent/hypoplastic pulmonary artery.
Diaphragmatic Hernia
  • L > R more common in the left side
  • If large hernia in early neonatal period may lead to opaque hemithorax
  • Bochdalek hernia—posterolaterally due to persistent pleuroperitoneal canal
  • It may contain fat, omentum, spleen, kidney and bowel—Associated with pulmonary hypoplasia and contralateral mediastinal shift113
  • In older age group—hemithorax not opaque due to gas in bowel loops.
  • Parenchymal opacification caused by replacement of air in the distal air spaces by fluid (transudate, exudate or blood) or tissue (e.g. bronchoalveolar cell carcinoma, lymphoma) is defined as consolidation
  • Usually no volume loss
  • Expansile consolidation Pneumococcal and Klebsiella pneumonia
    • Neoplasms
    • Air bronchogram.
Pleural Thickening
If extensive—may lead to opaque hemithorax
  • Previous thoracotomy
  • Empyema
  • Hemithorax
  • Viewed en profile–appears as a band of soft tissue density.
  • En face—ill-defined veil-like shadowing
  • USG—not so sensitive pleural thickening, not reliably detected unless 1 cm in thickness
  • CT—very sensitive
  • May calcify, involve visceral pleura
  • If entire lung is surrounded by fibrotic pleura—Fibrothorax.
Fibrothorax is defined by Criteria
  • If uninterrupted pleural density that extends over at least a forth of the chest wall
  • On CT—8 cm craniocaudal
    • 5 cm laterally
    • 3 mm thick
  • No mediastinal shift
  • Reduced ventilation due to decrease in volume114
  • If on X-ray—decreased vascularity, significant ventilatory restriction is present
  • Surgical decortication is required.
More common primary pleural malignancy
  • Prolonged exposure to asbestos dust—crocidolite (MC)
  • Nodular pleural thickening ± hemorrhagic pleural effusion around all or part of lung.
With central mediastinum
Volume loss due to ventilatory restriction
  • Bronchial stenosis by tumor compression at hilum
  • Malignant pleural thickening is nodule and extends into fissures or over the mediastinal surface, may surround whole lung
  • MRI better than CT in assessing involvement of mediastinum and chest wall. Signal intensity slightly more than muscles on both T1 and T2 WI.
  • 2–3 months after surgery
  • H/o of pneumonectomy
  • ± Rib resection
  • ± Opaque bronchial sutures.
  1. Faulty radiologic technique
    • Overpenetrated films
  2. Decreased soft tissues
    • Thin body habitus
    • Bilateral mastectomy115
  3. Cardiac causes of decreased pulmonary blood flow
    • Right to left shunts (Tetralogy of Fallot, Ebstein's malformation, Tricuspid atresia)
    • Eisenmenger physiology
  4. Pulmonary causes of decreased pulmonary blood flow
    • Pulmonary embolism
    • Air trapping
    • Emphysema
    • Bulla
    • Bleb
    • Interstitial emphysema.
  1. Faulty radiologic technique
    • Rotation of patient
  2. Chest wall defects
    • Mastectomy
    • Poland syndrome (absence of pectoralis major)
  3. Air trapping
    • Extrinsic compression of main bronchus
    • Endobronchial obstruction
    • Bronchiolitis obliterans
    • McLeod syndrome
    • Emphysema
    • Pneumothorax
  4. Vascular causes
    • Pulmonary arterial hypoplasia
    • Pulmonary embolism
    • Congenital lobar emphysema (Fig. 1.29)
    • Compensatory over-aeration.
Tetralogy of Fallot
  • Congenital disease presenting as left to right shunt with four components VSD, infundibular narrowing of the right ventricular outflow tract, right ventricular hypertrophy, overriding aorta.116
zoom view
Fig. 1.29: Anteroposterior radiograph of chest shows congenital emphysema of left lung with herniation to right side midline
Plain Skiagram Chest
  • Boot-shaped heart
  • Hypoplasia of pulmonary artery
  • Pulmonary oligemia leading to translucent lungs
  • Right-sided aortic arch.
  • Discontinuity between anterior aortic wall and IV septum due to overriding aorta
  • Small left atrium
  • RV hypertrophy with small outflow tract
  • Doppler USG can quantify severity of VSD and pulmonary stenosis.117
Ebstein's Anomaly
  • Congenital disease with left to right shunt with atrialization of right ventricle due to downward displacement of the dysplastic incompetent tricuspid valve leading to a small right ventricle. There is associated ASD or PDA
  • Patient presents early reversal of the shunt from right to left, leading to cyanosis.
Plain Skiagram Chest
  • Massive globular “funnel-like” cardiomegaly with small pedicle due to hypoplastic aorta and pulmonary trunk (the only CHD with this feature)
  • Extreme RA enlargement
  • Dilated IVC and azygous vein
  • Severe pulmonary oligemia leading to translucent lung fields
  • Calcification of tricuspid valve may occur.
  • Large sail-like tricuspid valve
  • RA enlargement
  • Doppler USG can quantify tricuspid regurgitation.
Tricuspid Atresia
  • Congenital disease with atresia of the tricuspid valve and pronounced cyanosis at birth and is associated with ASD and a small VSD. Pulmonary stenosis may or may not be present. It may present with or without transposition of great vessels.
Plain Skiagram Chest
  • Left ventricular contour of the heart with rounding due to both enlargement and hypertrophy of left ventricle
  • RA enlargement
  • Concave pulmonary bay
  • Pulmonary oligemia leading to translucent lung fields.118
Eisenmenger Physiology
  • Occurs when there is reversal of left to right shunt as a consequence of pulmonary arterial hypertension.
Plain Skiagram Chest
  • Pronounced dilatation of central pulmonary arteries
  • Pruning of peripheral pulmonary arteries leading to increased translucency
  • Enlargement of RV
  • Return of LA and LV to normal size
  • Normal pulmonary venous pressure.
Pulmonary Embolism
  • The embolism is usually a result of DVT in the lower limbs
  • There is a classic triad seen in 33% of cases of hemoptysis, pleural rub and thrombophlebitis
  • Hypertranslucency is seen bilaterally in cases presenting with acute massive embolic episode, which blocks the main pulmonary artery before the development of infarction. The development of infarction leads to segmental, lobar or wedge-shaped areas of consolidation. Pleural effusion is usually present
  • Unilateral hypertranslucency may occur in cases where the embolus blocks one of the major pulmonary arteries.
Air Trapping
  • There is trapping of air in the lungs due to valve mechanism acting at the level of the trachea or major bronchi
  • In children, this is usually due to a foreign body. In adults, an endotracheal or endobronchial growth of extrinsic pressure is the usual cause
  • On plain skiagram chest, there is hypertranslucency with evidence of increased volume like splaying of ribs, long tubular heart, barrel-shaped chest due to increased AP diameter of the 119chest and depressed domes of diaphragm. These findings may be unilateral or bilateral depending on the etiology. However, in unilateral increase in volume, these findings are unilateral except for the contralateral shift of mediastinum and largely normal cardiac contour
Bulla, Blebs and Pneumatoceles: When very large, it may compress the surrounding normal lung and may lead to either unilateral or bilateral hypertranslucency.
Bronchiolitis obliterans: Also known as constrictive bronchiolitis or obliterative bronchiolitis is a result of inflammation of bronchioles leading to obstruction of bronchial lumen.
  • Chest X-ray may be normal
  • Hyperinflated lungs leading to increased lucency may be seen in upto 60% of cases
  • There is decrease in pulmonary blood flow
  • On HRCT, there is mosaic perfusion and lobular air trapping may be seen, bronchial wall thickening and bronchiectasis may also be seen.
McLeod syndrome: Also known as Swyer-James syndrome, it is a result of acute viral bronchiolitis in infancy, leading to constrictive bronchiolitis.
  • There is increased translucency of the affected lung
  • Small hemithorax with decreased or normal volume of the lung
  • Air trapping during expiration
  • Small ipsilateral hilum
  • Reduced pulmonary vasculature with pruning of vessels.
Emphysema: This term is broadly used to define pulmonary diseases characterized by permanently enlarged air spaces distal to terminal bronchioles accompanied by destruction of alveolar walls and local elastic fiber network.
Plain Skiagram Chest
  • Hyperinflated translucent lungs
  • Low or flat hemidiaphragms
  • Increased retrosternal air space120
  • Barrel chest
  • Pulmonary vascular pruning
  • Right heart enlargement
  • Bullae.
Compensatory Emphysema or over-aeration is a distinct clinical entity where there are unilateral findings of emphysema seen due to diseased non-functional contralateral lung.
  • Can be unilateral or bilateral and is a result of collection of air in the pleural cavity.
Plain Skiagram Chest
  • There is increased translucency with loss of broncho-vascular markings
  • There is contralateral shift of mediastinum in the unilateral types
  • In tension pneumothorax, there may be inversion of diaphragm.
Congenital Lobar Emphysema
  • Result of congenital insult leading to constriction of bronchi supplying one lobe leading to air trapping and increase in volume
  • The enlarged lobe compresses the remaining normal lobes
  • Contralateral mediastinal shift.
Pulmonary Arterial Hypoplasia
  • Small or absent main pulmonary artery
  • Concave pulmonary bay
  • Pulmonary oligemia.
Causes of Bilateral Hypertranslucency
Faulty Radiologic Technique
  • Overpenetrated film.
Decreased Soft Tissues
  • Thin body habitus
  • Bilateral mastectomy.
Cardiac Cause
  • Right to left shunt
  • Eisenmengerization of left to right shunt.
Pulmonary Cause
  • Decreased vascular bed
    • Pulmonary embolus.
  • Increase in air space
    • Air trapping—asthma, acute bronchitis, emphysema
    • Bullae, blebs
    • Interstitial emphysema.
Localized Lucent Lung Defect
  • Cavity
    • Infection
    • Neoplasm
    • Vascular occlusion
    • Inhalational – Silicosis with coal worker's pneumoconiosis.
  • Cyst
    • Cystic bronchiectasis
    • Pneumatocele122
    • Centrilobular/bullous emphysema
    • Honeycomb lung
    • Diaphragmatic hernia
    • CCAM Type I, CLE, bronchogenic cyst.
Hyperlucent lung: (Unilateral):
Increased density contralateral lung
Overpenetrated film
Overpenetrated film
Rotation, scoliosis
Soft tissue
Congenital absence of pectoralis major
Poliomyelitis (Poland's syndrome)
Compensatory: Lobar collapse,
Obstructive: Foreign body, tumor
McLeod's syndrome.
Absent/hypoplastic pulmonary
artery, obstructed pulmonary artery
< Tumor embolus
McLeod's syndrome
Tuberous sclerosis
Rheumatoid disease
Fibrosing alveolitis
Similar appearance
Connection with bronchus +
Cystic fibrosis
Pancreatic anomalies +
Upper zones
Extrinsic allergic alveolitis
Upper and midzones bases
Cystic bronchiectasis
Cryptogenic fibrosing alveolitis
Mid and bases
Multiple Pinpoint Opacities
Iodized oil emboli. Contrast medium is seen at the site of termination of the thoracic duct
Located in upper and mid zones, seen in gold miners
Evenly distributed throughout the lung with Kerley A and B lines
Inhalation of barytes
Very dense, discrete opacities
May be slightly larger in size
Bases and apices are spared
Alveolar microlithiasis
Familial, black pleura, enlarged heart size is positive.
Lobar Pneumonia (Fig. 1.30)
Consolidation involving the air spaces of an anatomically recognizable lobe. The entire lobe may not be involved and there may be a degree of associated collapse.
  1. Streptococcus pneumonia: Commonest cause, unilobar in distribution. No cavitation. Little or no collapse. Pleural effusion is uncommon.
  2. Staphylococcus: Especially in children. Sixty percent develop pneumatocele. No lobar predilection, effusion, empyema and pneumothorax and bronchopleural fistulae are common.124
    zoom view
    Fig. 1.30: Posteroanterior radiograph of chest shows left lower lobe consolidation collapse
  3. Klebsiella pneumoniae: Multilobar involvement, cavitation and lobar enlargement is common.
  4. Tuberculosis: Associated collapse is common.
    Right lung is more frequently involved.
    Anterior segment of the upper lobe and the medial segment of the middle lobe are the commonest sites.
  5. Streptococcus pyogenes: Lower lobe predominates, often associated with pleural effusion.
Consolidation with Bulging Fissures
Homogeneous or inhomogeneous air space opacification with bulging of the bounding fissures
  1. Infection with abundant exudates
    Klebsiella, Streptococcus pneumoniae, Tubercular bacilli
  2. Abscess: When air-area of consolidation breaks down.
    Common organisms include Staphylococcus aureus, klebsiella and other gram –ve organism
  3. CA of the bronchus.125
Lung Disease Associated with Honey Combing
Collagen Disorders
Rheumatoid lung
: Basal predominance
Infiltrates and effusion are common
Scleroderma basal
Preceded by fine, linear basal streaks.
Extrinsic allergic alveolitis upper zones
Sarcoidosis sparing of extreme apices
  • Hilar lymph adenopathy
  • Egg shell calcification.
: Mainly due to asbestosis
Cystic bronchiectasis lower and middle zones
Bronchial wall thickening
Localized areas of consolidation
Histiocytosis—mid and upper zones.
  • Disseminated nodules followed by honeycomb pattern
Tuberous sclerosis
: Rare
: Rib notching +
Ribbon ribs +
  1. A generalized reticular pattern or miliary mottling which when summated produces the appearance of air containing ‘cysts’ 0.5–2 cm in diameter.
  2. Obscured pulmonary vasculature.
  3. Late appearance of radiological signs after the onset of symptoms.
  4. Complications
    1. Pneumothorax is frequent
    2. Cor pulmonale later in the course of the disease.126
  1. Collagen diseases—Rheumatoid arthritis
  2. Extrinsic allergic alveolitis
  3. Sarcoidosis
  4. Pneumoconiosis
  5. Cystic bronchiectasis
  6. Cystic fibrosis
  7. Drugs—nitrofurantoin, busulfan, cyclophosphamide, bleomycin and melphalan
  8. Langerhans cells histiocytosis
  9. Lymphangioleiomyomatosis
  10. Tuberous sclerosis
  11. Idiopathic interstitial fibrosis (cryptogenic fibrosing alveolitis)
  12. Neurofibromatosis.
Rheumatoid Arthritis
  • Most pronounced at the bases
  • It's severity does not parallel to that of joint involvement
  • In the earlier stages, it is characterized by radiologic appearance of patchy area of air space consolidation (multifocal ill-defined densities)
  • In the intermediate stage, there is fine reticular pattern or reticulonodular pattern
  • As the progress decreases, there is appearance of cystic spaces of honeycomb lung
  • All the above features may be preceded by basal infiltrates ± small effusion.
  • Predominantly basal
  • Less regular ‘honeycomb’ pattern which is preceded by fine, linear, basal streaks, cor pulmonale is unusual127
  • Other clinical signs which include skin changes, soft tissue calcification, disturbances of esophageal motility and dilatation of the esophagus
  • Radiologically, an upper GIT series may demonstrate both esophageal dilatation and decreased motility as well as small bowel dilatation.
  • It produces a basilar distribution that may progress from a fine reticular interstitial pattern to a coarse interstitial pattern with honeycombing
  • The basilar reticular or honeycomb pattern is also frequently associated with pleural thickening, pleural calcification.
  • It has predominant upper lobe distribution
  • It may be associated with hilar or mediastinal lymphadenopathy with pleural thickening. The fine reticular pattern is seen which progresses to honeycomb lung.
Extrinsic Allergic Alveolitis
  • Predominantly seen in the upper lobes of the lung.
Sparing of extreme apices:
  • Honeycombing of the lung is usually preceded by some classic finding including hilar adenopathy and an interstitial nodular or fine reticular interstitial pattern
  • As the interstitial disease, progresses, there is regression of hilar adenopathy.128
Langerhans Cell Histiocytosis
  • ‘Honeycomb’ pattern preceded by disseminated nodules
  • May be predominantly in the mid and upper zones
  • Cor pulmonale is uncommon.
Usual Interstitial Pneumonitis/ Cryptogenic Fibrosing
  • More marked in the lower lobes of the lungs initially and progresses to involve the whole of the lungs
  • In HRCT, there is honeycombing and fibrosis. It shows a uniform and patchy distribution.
Tuberous Sclerosis
  • Symptoms, when they appear, usually first appear in adult life
  • Pneumothorax, pulmonary insufficiency and cor pulmonale may complicate the syndrome
  • The clinical and radiological manifestation of the disease in the brain, kidneys and skin readily establishes the diagnosis.
  • Honeycomb lung ± rib notching ribbon ribs and/or scoliosis is seen in 10% cases but not before adulthood.
  • Serous membrane which covers the surface of lung and lines the inner surface of chest wall.
Common conditions are:
  • Pleural effusion
  • Pleural thickening129
  • Pneumothorax
  • Pleural masses
  • Pleural calcification.
Pleural Effusion
May be transudate, exudate, pus, blood or chyle.
Contain < 3 g/dL of protein, usually bilateral
  1. Increase hydrostatic pressure
    Main cause is congestive cardiac failure (CCF)—1st on right side and then bilateral, constrictive pericarditis.
  2. Decrease colloid osmotic pressure
    • Decrease protein product—cirrhosis with ascites
    • Protein loss/hypervolemia
      Nephrotic syndrome
      Peritoneal dialysis
  3. Meig-Salmon syndrome
    Ovarian fibroma, thecoma, GCT, Brenner's tumor, etc.
    • Ascites
      Pleural effusion resolves with tumor removal.
Increased permeability of abnormal pleural capillaries with release of high-protein fluid into pleural space.
> 3 g/dL of protein.
  1. Infection
    1. Empyema—Pleural effusion with presence of pus. +/− positive culture.
      Micro-organisms are anerobic bacteria
      Gross pus (WBC >15000/cm3)
    2. Parapneumonic effusion—Less with pneumonia, abscess, bronchiectasis.130
    3. TB—Increase protein content >75 g/dL
    4. Fungi and parasite—Amebiasis, secondary to liver abscess.
  2. Malignant disease—Lung carcinoma (Ca), lymphoma, breast, ovarian Ca and malignant mesothelioma. Positive cytological result.
  3. Vascular—Pulmonary embolism (15–30%)
  4. Abdominal disease
    Left side pleural effusion (68%),
    right side (10%).
    Boerhaave's syndrome:
    Left side
    Pleural effusion—79%
    Elevation and restriction of
    diaphragmatic movement
    Plate-like atelectatic or pneumonia.
  5. Connective tissue disorder.
    RA—UL(R>L) recurrent alternating sides relatively unchanged in size for months.
Systemic Lupus Erythematosus (SLE)
Bilateral (B/L) in 50% (L>R), increased cardiac size.
Wegener's Granuloma
  • Bleeding into the pleural space may be trauma.
  • Hemophilia or excessive anticoagulation—Rare
  • Pulmonary infarction—Blood stained
  • Lung carcinoma—Blood stained.
Chyle is milky fluid high in neutral fat and fatty acid.
Secondary to damage or obstruction of the thoracic lymphatic vessels.131
Causes: Most common cause—trauma—surgery.
Carcinoma of lung, lymphoma, filariasis.
Radiological Features
Plain film: Frontal view less sensitive < Lateral view < Lateral. decubitus view.
  • Moderate effusion with mediastinum is shifted towards the side of collapse—likely due to carcinoma of bronchus
  • Empyema may be suspected by the appearance of a fluid level
  • Septations.
Ultrasonography (USG)
Very sensitive, can detect few ml of fluid.
Transudate—Clear fluid separating the visceral and parietal pleura
Moving lung suspended within the pleural space.
Exudate—Echogenic fluid, containing floating particulate material, septations or fibrin strands may be associated with pleural nodule or thickening > 3 mm.
CT—Simple pleural effusion—Sickle-shaped disease in the most dependent part of thorax posteriorly
  • In regard to tissue density—CT is rarely helpful, however
  • Exudate—>water density septation
  • Parietal pleural thickening on CECT
  • Extrapleural fat thickening of >2 mm
  • Chylous—Decreased density than H2O.
Acute hemorrhaged—Increased density of fluid with presence of fluid-fluid level.
Pleural Thickening
  • Non-pathological
    B/L apical pleural thickening, symmetrical
    Elderly patient
    Probably ischemia is the cause132
  • Trauma: If the entire lung is surrounded by the fibrotic
    Fibrothorax is secondary to organized effusion, hemothorax or pyothorax
  • Dense fibrous layer of 2 cm thickness almost always on visceral pleura
  • Frequent calcification on inner aspect of pleura.
  • Chronic empyema—H/o pneumonia with presence of parenchymal scars. Usually seen over the bases
  • Frequently a thickened layer of extrapleural fat can be seen separating the parietal and visceral layer
  • Calcification may be seen.
Tuberculosis (TB)
  • Lung apex
  • Can be associated with apical cavity
  • Calcification may be seen.
Inhalation Disorder
Asbestos exposure involves the lower lateral chest wall, basilar interstitial disease.
Pleural plaque: Involves the parietal pleura with sparing of visceral pleura.
Asymmetric apical pleural thickening may represent Pancoast tumor destruction of adjacent ribs and spine penetrated film will be helpful.
  • Metastasis—often nodular.133
Pleural Calcification
Has the same causes as pleural thickening.
Unilateral (U/L) pleural calcification—result of previous empyema, hemothorax or pleurisy and also occur in visceral pleura associated with pleural thickening.
  • Calcification may be in a continuous sheet or in discrete plaque.
    Bilateral (B/L) calcification seen in asbestos exposure, more delicate, frequently visible over the diaphragm and adjacent to axilla located in parietal pleura.
Pleural Masses
  • Incomplete border and tapered superior and inferior borders
  • Usually make obtuse angle with chest wall
  • Displacement of adjacent lung parenchyma with compressive atelectasis and blowing of bronchi and pulmonary vessels around the mass
  • Vanishing tumor and encysted pleural effusion fluid may become loculated in interlobar fissure seen in heart failure lateral film typical lenticular configuration. Encysted pleural effusion—often associated with free pleural effusion
  • Water density
  • Neoplasm.
  • Lipoma—CT detects the origin of mass of fat density.
    Benign lipoma confirms fat density with few fibrin strands
  • Thymolipoma, angiolipoma, teratoma, characterized by islands of soft tissue density, interspersed with fat
  • Fibroma/benign fibrous mesothelioma—Most common benign tumor may be associated with hypoglycemia and HPOA solitary lobulated non-calcification mass
    If pedicle is seen—diagnostic, shape changes with the change in patient's position.
Malignant Pleural Thickening
Bronchogenic Carcinoma: Most common cause.
When a bronchogenic carcinoma involves the pleura diffusely with resultant pleural effusion, the tumor is considered unresectable.
Malignant Mesothelioma
  • Rare tumor
  • 70% of cases—H/O asbestos exposure
  • Nodular pleural thickening around all or part of lung with pleural effusion
  • Pleural—plaque
  • Metastatic disease—Breast and gostrointestinal tract (GIT)
  • Most common manifestation is malignant pleural effusion
  • Pleural thickening is nodular and frequent. Encase the entire lung including mediastinum
  • Pleural lymphoma
  • Pleural effusion
    CT= localized broad-based lymphomatous pleural plaque.
Spontaneous—Most common type
M:F: 8:1, young male with tall thin stature
Due to rupture of a congenital pleural bleb, such blebs are usually in the lung apex and may be B/L.
Iatrogenic— For example, postoperative, after chest aspiration during artificial ventilation, after lung biopsy.
Traumatic—result of a penetrating chest wound, closed chest trauma, associated finding like rib fracture.
Surgical/mediastinal emphysema
Secondary to lung disease:
  • Emphysema
  • Chronic bronchitis135
  • Common factor in an elderly patient
  • Rupture of a tension cyst in Staphylococcus pneumoniae
  • Rupture of a subpleural TB focus
  • Rupture of a cavitating subpleural metastases
  • Pneumoperitoneum—air passes through a pleuroperitoneal foramen
  • Generalized
  • Localized—if pleural adhesions are present.
If air can move freely in and out of pleural space during respiration.
If no movement.
Valvular: If air enters the pleural space on inspiration but does not leave on expiration, it is valvular—as intrapleural pressure increase it leads to development of tension pneumothorax.
Radiological features: Small pneumothorax in an erect patient collects at the apex.
Expiratory film—useful in closed pneumothorax.
Lateral decubitus film with affected side uppermost.
Tension Pneumothorax: Massive displacement of mediastinum.
  • Kinking of great veins
  • Acute cardiac and respiratory embarrassment
  • Ipsilateral lung may be squashed against the mediastinum and herniate across the midline
  • Depression of ipsilateral diaphragm.
    Loculated pneumothorax = pleural adhesion may result in loculated pneumothorax.
    D/D—subpleural bullae, thin-walled pulmonary cavity/cyst.
    Few linear strands can be seen in these but not in pneumothorax.
    Hydropneumothorax containing a horizontal fluid level (Fig. 1.31).
zoom view
Fig. 1.31: Posteroanterior radiograph of chest shows hydropneumothorax on left side with mediastinal shift to right side
Radiological Appearances of Pleural Fluid
  • Most dependent recess of the pleura is the posterior costophrenic angle (100–200 mL of fluid is required to fill this). Small effusions are hence seen earlier on a lateral film and now on ultrasound.
  • Decubitus view with a horizontal beam is being the most sensitive view
  • The effusion casts a homogeneous opacity spread upwards. Typically, this opacity has a fairly well-defined, concave upper edge, which is higher laterally than medially and obscures the diaphragmatic shadow
  • A massive effusion may cause complete radiopacity of a hemithorax.137
  • In the presence of a large effusion, lack of displacement of the mediastinum suggests that the underlying lung is completely collapsed
  • Lamellar effusions are shallow collections between the lung surface and the visceral pleura
  • Large effusions may accumulate between the diaphragm and the undersurface of a lung—this is called subpulmonary pleural effusion. The apex is more lateral than normal. This collection moves fully with changes of posture
  • Empyema usually has a lenticular shape, irregular thick walls and may compress the underlying lung
  • Loculated effusions tend to have comparatively little depth, best considerable width, rather like a biconvex lens.
Pneumothorax (Fig. 1.32)
It collects in a free pleural space in an erect patient at the apex. On the frontal film, sharp white line of the visceral pleura will be visible, separated from the chest wall by the radiolucent pleural space, which is devoid of lung markings.
An expiratory film will make a closed pneumothorax easier to see since on a full expiration, the lung volume is at its smallest, while the volume of pleural air is unchanged.
In tension pneumothorax, the ipsilateral lung may be squashed against the mediastinum, or herniate across the midline, and the ipsilateral hemidiaphragm may be depressed.
Nodular extension into the fissures, pleural effusion, and volume loss of the ipsilateral lung, all suggest malignancy.
Metastatic: The most frequent primary tumors being of the bronchus and breast.
Mesothelioma: Well-defined, lobulated mass adjacent to chest wall, mediastinum, diaphragm.138
zoom view
Flow chart 1.2: Pleural Lesions
Lipoma: Well-defined, lobulated mass may change shape with respiration on CT, presence of fat is diagnostic.
Mesothelioma: Due to prolonged exposure to asbestosis.
Nodular pleural thickening with pleural effusion. Rib involvement may occur, but is rare.
The common conditions are:
  1. Old empyema
  2. Old hemothorax
  3. Asbestos inhalation
  4. Silicosis.
Old Empyema and Old Hemothorax
  • Calcification is irregular, resembles a plaque or sheet and is contained within thickened pleura
  • En face, it is hazy and veil-like but in profile, it is dense and linear, paralleling the chest wall
  • Usually unilateral
  • Most common site: Lower posterior half of chest
  • In tuberculous empyema—both visceral and parietal pleura may be calcified, which are sometimes separated by a soft tissue opacity which may contain fluid.
Asbestos Inhalation
  • A feature of asbestosis is pleural plaque which is a well-defined soft tissue sheet originating in the parietal pleura (latent period is 10 years).
  • Latent period for calcification to develop is 20 years
  • Lesions are usually bilateral, lying in the middle zone, lower zone and diaphragm.
    When calcified, ‘holly leaf pattern’ with sharp and often angulated outlines and often follow the margins of the ribs.140
    zoom view
    Fig. 1.32: Posteroanterior radiograph of chest shows loculated pneumothorax in left lower hemithorax causing compression atelectasis of left lower lobe
  • Usually <1 cm thick.
    Diffuse pleural thickening: Unlike pleural plaques, the margins are well-defined and tapered; may reach several cm in thickness.
    Pleural effusion—Uncommon.
Malignant Mesothelioma
Latent period: 40 years
Pulmonary changes: (peripheral lower zone)
  • Fibrosis
  • Bronchial carcinoma
  • Pseudotumor (fibrotic atelectasis).
Extrathoracic Manifestation
Peritoneal mesothelioma, malignancy of upper GIT.
  • Inhalation of silica (SiO2)
  • Pleural calcification is similar to asbestosis.
Other Features
  • Multiple small nodules in upper zone and middle zone
  • Hilar lymph nodes with egg shell calcification
  • Progressive massive fibrosis
  • Caplan's syndrome also occurs in patients with rheumatoid arthritis and silicosis.
Peripheral, Base
  1. Cryptogenic fibrosing alveolitis
Ground glass appearance
Subpleural reticular shadows
Reticulations extend centrally
Small cyst formation, commencing at subpleural site.
  1. Asbestosis
Changes are seen at the lung base.
Thickened curvilinear, subpleural
lines are seen.
Thickened subpleural septal lines,
coarse parenchymal lines extending centrally.
Rounded atelectasis with comet
tail sign
Central Upper Fluid Zones
Sarcoidosis: Thickened bronchovascular markings with perivascular beading present centrally.
Patchy alveolar opacification.
Subpleural and peribronchovascular nodules.
Peripheral and Central
Bronchovascular markings and septal line thickening.
No alveolar opacification is seen.
: Characteristic widespread distribution.
More common in women.
Uniform-sized well-defined cysts with normal parenchyma surrounding them.
Tuberous Sclerosis
Variable-sized cyst
No feminine predilection.
  1. Fat Density
    1. Epicardial Fat Pad
      • Obese, Cushing's syndrome
      • Uncapsulated, homogeneous extrapleural fat.
    2. Lipoma
      • Uncommon, well-defined, encapsulated thin fibrous septae.143
        zoom view
        Flow chart 1.3: Pleural Calcification
    3. Liposarcoma
      • Ill-defined
      • Inhomogeneous.
    4. Morgagni hernia.
  2. Soft Tissue
    Lymph nodes
    • Lymphoma
    • Carcinoma—breast, lung, colon
Traumatic—Diaphragmatic hernia
  • H/O trauma
  • Mostly left sided
  • Single entry and exit
  • Barium or other studies—useful in diagnosis
Diaphragmatic hump
  • Herniation of liver through the gap
  • Liver scan or USG144
Fibrous tumors of Pleura
  • Pleura-based, well-defined, homogeneously enhancing, stalked.
Primary or Secondary Malignancy
  • Well-defined smoothly marginated lung-based.
Cystic or Vascular
  • Pericardial cyst
  • Well-defined, round to oval, fluid density, non-enhancing, right CP angle.
Hydatid cyst
  • Unilocular, associated with hepatic cyst or may be bilateral
  • Meniscus sign, water lily sign
  • Loculated pleural effusion
  • USG—makes the diagnosis
  • Varices
  • Delayed phase scanning is needed
  • Portal hypertension, more on right
  • Scimitar syndrome
  • Abnormal vessel draining into IVC or hepatic vein
  • Lobar agenesis or aplasia
  • Accessory diaphragm, pulmonary sequestration.
Pericardial cyst
  • Etiology—embryogenesis, parietal recess, diverticulum, sequelae
  • 30–40 years, asymptomatic
    Plain film chest—well-defined, round to oval mass
  • Cardiophrenic angle mass usually right
  • Changes shape with respiration and body position.
Well-defined, anechoic to hypoechoic, no septae145
Computer Tomography (CT)
  • 3–8 cm in size
  • May extend into fissures
  • No enhancement, no perceptible wall.
Hydatid Cyst
  • Three layers—Adventitia, friable ectocyst, inner germinal layer
  • Lung cyst—Unilocular, 20% bilateral, 10% associated with hepatic cyst
  • Well-defined, round-oval, homogenous masses upto 10 cm in diameter
  • Calcification is rare
  • Meniscus sign, water lily sign.
Morgagni Hernia
  • Defect between septum transversum and right and left costal margins of diaphragm
  • Usually asymptomatic, more common in obese people
  • Right-sided, small lesions may only have omental fat, and then it may be difficult to distinguish from epicardial fat pad
  • Large lesion—colon, liver, stomach or small intestine may herniate
  • Barium study—tenting of colon or loop above the diaphragm.
    CT—Omental fat, omental vessels and abdominal viscera are seen in the mass.
Diaphragmatic Hump and Hernia
  • Trauma—Hernia mostly seen on left side (posterior and central)
  • Colon or less commonly stomach are the contents
  • Barium—Entry and exit through the defect are closely apposed
  • Obstruction is frequent probably because of angular margins of the defect but are detected late because of subtle changes in plain film.146
  • On right side—Liver may herniate in severe trauma
  • A liver scan is helpful.
Congenital Hernia
  • More common on right side
  • It has a hernial sac.
Scimitar Syndrome
  • Presence of partial anomalous pulmonary venous return below the diaphragm, mostly right side
  • Lobar agenesis or aplasia, other systemic artery from aorta in lower thorax or upper abdomen
  • Pulmonary artery may be small or entirely absent, accessory diaphragm, hepatic herniation, pulmonary sequestration.
Fibrous Tumors of Pleura
  • Solitary, sharply-defined, sometimes lobulated soft tissue pleural-based mass without evidence of chest wall invasion, homogenous enhancement
  • Pedicle or stalk—pathognomonic and indicator of benign lesion, mobility
  • May grow very large than obtuse or acute angle may be formed with pleura.
Primary or Secondary Carcinoma
  • Well-defined, smoothly marginated
  • Lung-based
  • Multiple.
zoom view
Flow chart 1.4: Cardiophrenic Angle Masses
zoom view
Epicardial Fat Pad
  • Excessive deposition of fat in mediastinum
  • Obese patient
  • Cushing syndrome or excessive corticosteroid intake
  • Uncapsulated and extrapleural fat.
  • Uncommon
  • Well-defined, encapsulated, generally homogenous
  • May contain thin fibrous septae
  • Inhomogenous, poorly-defined.
Lymph Nodes
  • Anterior diaphragmatic group of LN—2 nodes, <5 mm is normal.
Causes of enlargement are:
  • Unilateral or bilateral
    • Lymphoma
    • Lung, breast or colon cancer—metastasis.