INTRODUCTION
Abdominal pain is a very common symptom of presentation for patients admitted to the emergency department (ED) and represents a strong challenge for physicians and nurses involved in diagnosis and treatment. Incidence and clinical manifestations are both influenced by many demographic variables (age, gender, geography, etc.).
Although in most of the cases, it is not related to a serious disease, in some cases, it can be the only symptom of a potential rapidly evolved situation.
ETIOLOGY/CAUSES
Many intra-abdominal disorders cause abdominal pain and also several extra-abdominal diseases can present with abdominal pain. Some of these are immediately life-threatening, requiring rapid diagnosis and surgery. The knowledge of abdominal anatomy and its innervation helps for differential diagnosis, however, a systematic and logic approach, with a careful medical history and clinical evaluation, is fundamental. Focused clinical history and physical examination are able to place a right diagnostic hypothesis in 80% of patients with abdominal pain (Table 1). There are some alert signs and symptoms that must always be taken into careful consideration, because they probably underlie a serious condition (Table 2). Often a definitive diagnosis is impossible in the ED but the emergency physician has always to identify and rule out life-threatening clinical conditions. These include ruptured abdominal aortic aneurysm (AAA), perforated viscus, mesenteric ischemia, and ruptured ectopic pregnancy. Other diseases (e.g. acute appendicitis, acute diverticulitis, severe acute pancreatitis, and intestinal obstruction) are also serious and nearly as urgent.
PATHOPHYSIOLOGY OF THE CONDITION
The abdominal viscera are innervated by nociceptive fibers on the mesenteric surface and inside the wall of the hollow organs. These fibers are sensitive both to mechanical, mainly stretching, and chemical stimuli. They can produce deaf, subcontinuous, crampy, or violent pain.2
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The abdominal pain is divided into:
- Visceral: Usually secondary to stretching of hollow organs, twist or spastic contraction. It can be dull and continuous or colic, often located in the median site, as visceral innervation is bilateral, and it corresponds to the dermatome relative to the involved organ. Therefore, for the organs located above the Treitz ligament, it will be epigastric, for those between the Treitz and the hepatic flexure of the colon, it will be umbilical, and for the most distal organs, it will be hypogastric.
- Parietal: It is usually acute, due to direct irritation of peritoneum located above the involved organ. The parietal innervation is monolateral, so the pain will be well localized. Only when there is a widespread involvement of peritoneum, as for leak of gastric contents, blood, pus, or other, the pain will be extended to all the abdomen. The peritoneal irritation may cause a reflex contracture of abdominal muscles whereby the abdomen will become stiff and untreatable. The irritant reaction to organic or chemical substances is different, so that the peritonitic pain will be much more striking during gastric perforation with spreading of gastric acid than during colic perforation, with leaking of stool or blood.4
- Referred: Appears when the afferent fibers from an injured abdominal organ enter the spinal cord at the same level of somatic fibers coming from distant regions (for example, the gallbladder pain can be referred to the right shoulder).
CLINICAL PRESENTATION
Major diseases that cause acute abdomen of immediate surgical interest.
Acute Appendicitis
The inflammatory process is due to appendicular lumen obstruction, which can cause an increase in pressure within the lumen with consequent local circulatory dysfunction with ischemia of the wall (catarrhal or phlegmonous form) and necrosis. If perforation of the necrotic bowel wall occurs, appendicitis becomes complicated by perforative peritonitis, localized or diffuse (gangrenous or perforated form), generally caused by aerobic (Escherichia coli, Streptococcus, and Staphylococcus) and anaerobic (Bacteroides) bacteria superinfection.
In case of acute inflammation, there will be spontaneous, dull pain, which arises in the epi-mesogastric or periumbilical area. Later, when serosa involvement and peritoneal irritation develop, the pain is localized in the right lower abdominal quadrant. In addition, the pain is exacerbated by the cough and is not modified by body position changes. Vomiting is sometimes present and a low-grade fever (37–38°C) can be detected. Steadily, the patient loses appetite, so that the evaluation of this data is very important for diagnostic exclusion of appendicitis. At the physical examination, pain is evoked by palpating the right lower quadrant (RLQ), or more commonly, Blumberg's sign can be present, but Markle's sign is more sensitive to define a peritoneal irritation. Markle's sign, or jar tenderness, consists in the evocation of pain in RLQ by dropping from standing on the toes to the heels with a jarring landing. In case of suspicion, a white blood cell (WBC) count and C-reactive protein (CRP) detection should be tested since the concomitance of neutrophilic leukocytosis and elevated CRP significantly increases the possible diagnosis of appendicitis.
In the presence of a striking clinical picture, no further tests are necessary, but surgical advice must be activated as soon as possible. In less obvious cases, it is necessary to study the diagnosis more in depth. With an expert operator, ultrasonography (US) has a good specificity, but if this examination is not diagnostic or not reliable, a computed tomography (CT) scan of the abdomen and pelvis must be performed. Then, based on the evidence of direct examination, the radiologist will decide whether to complete CT using intravenous or oral contrast agent.
Intestinal Ischemia
Intestinal ischemia can present itself with three distinct syndromes, of which the first two generally have a favorable prognosis. The first syndrome is chronic mesenteric ischemia, determined by gradual reduction of blood supply to the affected intestinal tract, generally due to mesenteric vessels atherosclerosis. This condition is present with postprandial intermittent 5abdominal pain (angina abdominis). The patient is ill when he eats and consequently tends to reduce food intake and may appear debilitated to medical examination, also considering that elderly subjects are the most affected by the disease.
Ischemic colitis is caused by inadequate vascularization of some colon fragments, not necessarily on atherosclerotic basis, and generally starts as rectorrhagia rather than abdominal pain.
Acute mesenteric ischemia is due to acute thromboembolic occlusion of the celiac tripod, superior or inferior mesenteric artery, which leads to rapid necrosis of a no longer vascularized intestinal region, with subsequent development of a systemic toxic syndrome and exitus if not operated immediately.
The syndrome occurs more often in the presence of risk factors for ischemia. Most frequently, the symptom of onset is a severe periumbilical pain with an abdominal physical examination not proportional to the pain described by the patient. When the intestinal infarction has already been established, signs of peritoneal involvement are present. Rectal bleeding is rare.
Blood tests show signs of dehydration, metabolic acidosis, and multiorgan involvement when the situation is advanced, while in earlier stages, it is possible to detect leukocytosis or increase in D-dimer, but with little specificity. It is important to consider the risk factors and the onset symptoms, as the mortality once the intestinal infarction has been established is approximately 90%.
Acute Diverticulitis
About 30% of people over 50 years and 60% of those over 80 years of age have a diverticular disease that mainly affects the sigmoid colon. Diverticulitis is caused by the inflammation and perforation of the diverticulum, which can be circumscribed and buffered by the mesentery or can be opened with abscess formation or frank peritonitis. The patient presents with cramping abdominal pain, more frequently located in the left lower quadrant (LLQ), but in case of dolichocolon or diverticulosis of the ascending colon, the RLQ can also be affected. Nausea, vomiting, and anorexia are frequently associated. The diagnostic workup, in case of clinical suspicion of diverticular disease, involves a CT scan with intravenous or oral contrast medium (Fig. 1), while the colonoscopy is contraindicated when diverticular perforation is suspected. Uncomplicated diverticulitis can be managed at home with antibiotic therapy and liquid diet, while perforation with abscess or peritonitis requires immediate surgical evaluation.
Bowel Obstruction
Intestinal occlusion occurs when a mechanical block prevents progression of intestinal contents. This causes a bowel distension upstream from the obstruction due to the ingested air, the gases produced by the bacteria, and the endoluminal secretions. If the occlusion is not recognized and treated rapidly, ischemia and subsequent necrosis of the intestinal tract will develop. Table 3 lists the main causes of intestinal obstruction.6
Fig. 1: Contrast enhancement CT scan that highlights the presence of loose ileal loops and with hydroaerial levels, thickening of the wall of the sigma with air bubbles in its context, the surrounding liquid flap. The findings are compatible with a perforated diverticulitis.
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The abdominal pain is widespread and intermittent, the passage of feces and gases is absent but in the initial stages, diarrhea may be present, caused by the irritation of the mucosa. In advanced stages, vomiting will occur, which may be fecaloid due to bacterial activity.
At the physical examination, the abdomen is distended and painful and the bowel sounds could be increased with metallic sound, reduced or absent. If peritonitis occurs, the abdomen will be rigid with rebound tenderness present. Laboratory tests show hemoconcentration with possible electrolytic imbalances and renal insufficiency. The abdominal plain X-ray makes evident the presence of hydro-air levels, intestinal distention, and absence of air in the rectum (Figs. 2 and 3). The diagnostics can be completed with a CT-scan if the clinical condition allows it, which can identify the cause of the occlusion with an approximate sensitivity of 100%. In the event of intestinal obstruction, the surgical evaluation must be timely; however, it is essential to correct fluids and electrolytes imbalances and to decompress the bowel with a nasogastric tube.7
FIGS. 2A AND B: Plain X- ray of the chest and of the abdomen with evidence of perforation, with typical free gas between the hemidiaphragm and the bowel wall, and hydro-air levels.
Fig. 3: Plain X-ray of the abdomen with evidence of the classic signs of intestinal occlusion distension of ileal loops, presence of hydro-air levels, absence of air in the rectum.
RED FLAGS
- Signs of shock (e.g. tachycardia, hypotension, diaphoresis, and confusion)
- Severe pain
- Signs of peritonitis
- Abdominal distention
EVALUATION
Evaluation of mild and severe pain follows the same process, although with severe abdominal pain or important systemic impairment, therapy must precede the other steps, and includes early surgical consultation. Life-threatening conditions should always be ruled out before focusing on less serious diagnoses. In seriously ill patients with severe abdominal pain, an early surgical exploration may be appropriate. In less critical patients, observation and a diagnostic workup are generally the right choice.
History
A thorough history usually suggests the diagnosis. It is necessary to promptly investigate the symptomatology in particular with regard to onset, quality, duration, intensity, radiation, and relationship with meals, causes triggering or attenuating the symptomatology. Of particular importance are characteristics and pain location, associated symptoms, and duration. Concomitant symptoms such as fever, melena, mucus or blood in the stools, hematuria, vomiting, hematemesis, heartburn, nausea, diarrhea, constipation, jaundice, and weight loss help direct subsequent evaluation. Past medical history and medications are essential, taking care that anticoagulants can increase the chances of bleeding and hematoma formation and alcohol predisposes to pancreatitis. Use of nonsteroidal anti-inflammatory drugs is also associated to epigastric pain. Recent antibiotic use if patient experiencing diarrhea. Collect information on the known allergies, on the date and time of the last meal, on any travel and activity employment, and on the use of drugs of abuse.
It is necessary to consider that while in most of cases, an acute abdominal inflammatory process, so as an acute bleeding causes tachycardia, if the process affects the diaphragm wall and therefore, the terminations of the vagus nerve, the patient may have a normal or bradycardic heart rate.
Physical Examination
Vitals signs must be evaluated in all patients as well as level of consciousness. General appearance is important: a sick patient is anxious, pale, diaphoretic, or in obvious pain. The abdomen must be evaluated starting with inspection to evaluate skin color, palpation to check distention of obvious masses, and auscultation of bowel sounds. Decreased bowel sounds suggest functional ileus or mesenteric infarction while hyperactive bowel sounds are present in small bowel obstruction. Palpation starts gently, away from the area of referred pain, detecting areas of particular tenderness, as well as the presence of guarding, rigidity, and rebound (all suggesting peritoneal irritation) and any masses. Voluntary guarding can be diminished by asking patients to flex the knees. Distracting the patient with conversation may divert attention from the examination. The inguinal area and all surgical scars should be palpated for hernias. It is important to look for typical signs like Murphy sign, or stopping the breathing because of the intense pain evoked by palpation of the gallbladder; rebound, or Blumberg sign, indicative of peritoneal irritation, which consists in evoking release pain after 9deep palpation; the characteristics of the bowel signs. There are controversial opinions on the indication in literature to perform rectal exploration routinely in the patient with abdominal pain. In fact, sensitivity and the specificity of this maneuver are rather low, but the presence of blood in ampoule can suggest diagnosis such as diverticulitis, tumor, and intestinal ischemia, while rectal tenderness poses in differential diagnosis anal fissures, perirectal abscess, and prostatitis.
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It is important to consider all the extra-abdominal conditions that can present with abdominal pain (Table 4).
INTERPRETATION OF FINDING
Abdominal distention, vomiting, dullness at percussion, and high-pitched peristalsis strongly suggests bowel obstruction.
Severe pain in a patient with a silent abdomen who is lying as still as possible suggests peritonitis; whereas a patient who cannot sit or stand still suggests renal colic.
Back pain and migrant pain with shock suggests ruptured AAA, particularly if there is a tender, pulsatile mass.
Previous abdominal surgery makes obstruction caused by adhesions more likely. Advanced age, generalized atherosclerosis, and hypertension increases the possibility of myocardial infarction, aortic abdominal aneurysm, and mesenteric ischemia.
INVESTIGATIONS
Laboratory Tests
Blood tests in abdominal pain should be focused according to clinical evaluation, keeping in mind that specificity and diagnostic accuracy are low.
Among laboratory tests, it is important to include glucose, electrolytes, creatinine, and liver function tests.
A dangerous approach is to rely on “normal” blood test rather than to clinical evidence and avoid observation and reevaluation.
In case of women of childbearing age, pregnancy must be considered, both as cause of the pain (ectopic pregnancy) and for the treatment to use.
Finally, urinalysis, tested by multitask or laboratory, is a routine test: it provides data in suspicion of renal colic, urinary tract infections, or porphyria, to test ketonuria and glycosuria, and to define urine specific gravity.
Arterial blood gas analysis is essential for critically ill patients with abdominal pain: metabolic acidosis and hyperlactatemia, if combined with high levels of creatine phosphokinase and creatinine, must create the suspicion of a systemic involvement, a widespread and advanced pathologic process.
Role of Abdominal X-ray
A standing chest radiograph remains the primary investigation of choice for the detection of free intraperitoneal gas, and may detect lower lobar pneumonia.
Plain abdominal radiography should be used selectively in the event of suspected intestinal obstruction or perforation (see Figs. 2A and B).
In several studies, the use of abdominal X-ray as first diagnostic step for abdominal pain has shown a very low diagnostic power, being significant only for intestinal obstruction (see Figs. 2 and 3). In this situation, the sensitivity of abdominal X-ray is 65–90% while specificity is 50–80%. Therefore, even if the CT scan sensitivity and specificity are higher, in the suspicion of intestinal obstruction, the abdomen X-ray is a first level test.
Ingestion of foreign body is another indication for abdomen X-ray, that allows to evaluate the shape, the size, and the position in order to establish the subsequent procedures.
Several studies have shown a higher sensitivity of ultrasound in the suspicion of hollow organ perforation (US 90% vs abdominal X-ray 70%). The only limit is the operator skill.
Role of Ultrasonography and Computed Tomography
Abdominal, contrast enhancement CT scan is the examination with the highest specificity and sensitivity, but bedside ultrasound is now considered the first diagnostic approach in the ED. In most cases, the ultrasound abdominal examination is sufficient to diagnose diseases of the upper right abdominal quadrant (cholecystitis, cholangitis) and in the diagnosis of renal colic, urinary tract infections, and ectopic pregnancy. It is also the fundamental in the 11diagnosis of aortic syndrome, it is also the fundamental in diagnosis of aortic syndrome and also in diagnosing perforation and intestinal obstruction.
If the ultrasound examination is negative or nondiagnostic but the clinical presentation is persistently altered, it is necessary to perform an abdominal CT scan, generally with the contrast medium, except there are absolute contraindications (history of anaphylactic shock or severe renal impairment). In literature, it is shown that using this method of approach (CT execution to patients with nonconclusive ultrasound), it is possible to reduce the number of CT scan to less than 50%.
TREATMENT
It is still not uncommon to think that treating abdominal pain with analgesic can mask the clinical evidence. On the contrary, it has been widely demonstrated that a correct analgesia facilitates clinical evaluation because it makes the patient better and more collaborative to examination, thus reducing possible complications, increasing the sensitivity of instrumental investigations, without altering the objective framework.
The class of drugs most indicated in the treatment of acute abdominal pain is that are effective, almost without side effects and have an antidote if necessary. Nonsteroidal anti-inflammatory drugs, used extensively in past because considered “safer,” are actually burdened from important cardiovascular, gastrointestinal, and renal side effects, particularly in elderly patients. In mild-moderate abdominal pain can be used paracetamol as a first-choice drug.
Antibiotics are indicated in diseases such as peritonitis and abdominal sepsis, urinary tract infections, and pelvic inflammatory disease (PID). Particular attention must be reserved for spontaneous bacterial peritonitis due for gram-positive aerobes.
Remember two nonpharmacologic treatments: (1) nasogastric tube to decompress a bowel obstruction or to confirm a gastrointestinal bleeding and (2) urinary catheter in presence of bladder obstruction or to monitor urinary output in critically ill patient.
SUMMARY
Although patients with abdominal pain in most cases do not have a severe pathology, the symptom may accompany very serious and potentially deadly clinical conditions, if not recognized promptly. Approach to patient with abdominal pain is summarized in Flowchart 1.
The knowledge of abdominal anatomy and the careful evaluation of clinical signs and symptoms, together with a precise focused medical history, allows to correctly orient in the diagnosis in 80% of cases.
There are no specific laboratory tests for the various morbid conditions, but the laboratory investigation serves mainly to quantify the degree of systemic involvement of the disease.
The most cost-effective diagnostic-instrumental approach in terms of cost/benefit is represented by the execution of an abdominal focused ultrasound in all patients; abdominal CT scan must be performed only in case of nonconclusive ultrasound.12
Abdominal pain must be treated even before diagnosis, and the use of opioids is safe and recommended.
Also, fluids and electrolytes imbalance must be treated promptly while making the diagnostic workup.
When the diagnosis is uncertain but the patient is still symptomatic, it is often advisable and safe to keep patients under observation to evaluate the possible evolution. Keeping in mind that normal examinations do not exclude an abdominal serious process.
A plain X-ray of the abdomen, which is significant only in the suspicion of intestinal obstruction or perforation.