Clinical Practice and Surgery of the Colon, Rectum and Anus Sisir Kumar Saha
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Applied Anatomy of the Colon and the Rectum and Disease of the Colon1

 
A BRIEF DESCRIPTION OF SURGICAL ANATOMY AND PHYSIOLOGY OF THE COLON AND THE RECTUM
 
Anatomical Review of the Colon and its Surgical Importance
The large intestine begins from the cecum and ends at the anal orifice (Fig. 1.1).
The medial wall of the cecum is connected to the terminal ileum and its bottom to the appendix. The large intestine has three distinct anatomical names. They are known as colon, rectum and anus. Unlike the small intestine, the longitudinal fibers that appear to be like a thin ribbon are present on the external wall of the colon and are located at three sites of its circumference. They are known as taeniae coli. They begin from the base of the appendix and are shorter in length than the true length of the colon, thus forming sacculations or outpouching between the taeniae coli. Apart from the taeniae coli, the colonic wall is constructed by the circular smooth muscles that keep protruding outwards between the taeniae coli. Its significance is to make a large mucosal surface area of the colonic wall that would provide a greater absorbing power of fluid that is discharged through the ileocecal valve.
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Fig. 1.1: The anatomical features of the large intestine
As a result, the loose motion tends to be semisolid, as they are pushed further down the colon and these feces are held in these sacculations a bit longer in contact with the colonic mucosa. The main purpose is to delay in transit, thus enhancing the absorption of water from the feces.
The taeniae coli are absent in the appendix, rectum and anus, but the longitudinal fibers cover all around the circumference of the appendix, rectum and anus. Its physiological function will be touched in brief in the respective section.
The ileocecal junction has a valve that regulates the discharge of the liquid motion from the terminal ileum to the cecum. It remains closed as a rule that allows the small intestine to absorb the bile salts, vitamins, and all other nutritional materials. The ileocecal valve opens up briefly at the force of the peristaltic waves— thus permitting the liquid materials from the terminal ileum into the lumen of the cecum. Both ascending and descending colon remains in the retroperitoneal space, but the transverse and sigmoid colon has a mesentery. They are mobile.
The physiological importance of the sigmoid colon is to accommodate the excess lumps of feces that could not be pushed down through the rectum. Because of this reason, the sigmoid colon and its mesentery get elongated along its long axis as well as circumferentially. In certain cases, the sigmoid colon along with its long mesentery becomes folded, forming various shapes of loops in the lower abdomen.
 
THE RECTUM AND ANUS
The meaning of the word ‘Rectus’ in Latin is straight. This means the rectus abdominis muscle is consistent with the above meaning, but the true meaning of the rectum is not clear in 2Latin. This could be interpreted in the same way that it is also a straight tube, constructed with circular and longitudinal muscles. The rectum is the continuation of the sigmoid colon and it begins anatomically at the level of third sacrum. It is around 15 cm in length.
Unlike the sigmoid colon, it has no mesocolon, nor does it have appendices epiploicae, but three taeniae coli merge together in order to invest around the outer wall of the rectum. The longitudinal muscle fibers are inserted into four main sites. One set of the fibers is attached to the dentate line below the internal anal sphincter, another set that passes down between the internal and external sphincters descends further to be inserted into three directions; some of the fibers pass through the space between the superficial external sphincter and subcutaneous external anal sphincters, and other fibers pass over the subcutaneous external anal sphincter to be attached to the skin and a few strands pass down vertically to be attached directly to the skin of the anal verge.
The purpose of the longitudinal muscles of the rectum is to provide continuous support to the circular muscle uniformly all around and to sustain the intra-luminal pressure uniformly all around the rectal wall, when needed for discharging flatus or feces through the anus. These fibers play a major role in the operation of opening of the anal orifice during defecation.
However, the entire rectum remains in the retroperitoneal space and lies loosely attached to the fascia of Waldeyer by the areolar tissue. In the resection of the rectum, mobilization from this fascia becomes easier, and the posterior wall of the rectum comes off from the fascia of Waldeyer by just blind finger mobilization. The middle rectal artery that lies behind the rectum may cause some degree of bleeding, but the surgeon needs not to be alarmed, if there appears to be bleeding from the torn vessels. A detailed account about the resection of the rectum is available in the section of the rectal surgery.
The upper one-third of the rectum is covered by the peritoneum anteriorly and laterally but the middle-third is covered by the peritoneum only anteriorly. The lower-third of the rectum is devoid of peritoneal covering. The infraperitoneal part of the rectum, known as ampulla, which can distend all around rests upon the pelvic floor, formed by the levator ani muscle and the anococcygeal raphe. This could be the reason as to why the sacrum has been gradually tapered down towards the bottom thus making a large space available outside the rigid bony wall for the distention of the ampulla.
The pelvic peritoneum that covers the anterior wall of the middle-third of the rectum is reflected anteriorly to cover the back and dome of the bladder, forming rectovesical pouch in male and to cover the back of the upper vagina and uterus, forming rectouterine pouch, known as pouch of Douglas in female subject.
In some literature, contrary to the textbook of anatomy and surgery, mesorectum has been referred in the operation of sphincter-saving low anterior resection. But this literature has not produced any cadaveric specimen of the mesorectum to support the description.1 there is no conclusive evidence in the Human Anatomy to suggest that the rectum has mesorectum like mesocolon. Such evidence has been recorded over 100 years in the Gray's Anatomy2 and all other textbooks of anatomy.3 Here is the conclusive evidence in the whole specimen of the rectum, removed during the operation of abdominoperineal resection of the rectum which has no mesorectum (Fig. 1.2).4
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Fig. 1.2: Operative specimen of the rectum with no evidence of mesorectum
However, both upper and the lower end of the rectum lie in the same midline despite the fact that it is resting on the sacral curvature. In sagittal plane, the rectum has two curvatures, the proximal one is directed towards the left, and the lower one directed towards the right. In coronal plane, the rectum has three curvatures, but the proximal convexity is directed towards the left, the middle one to the right and the lower one towards the left of the midsacral line before it passes through the center of the pelvic floor.
These curvatures are formed because of disparity between the length of the sacrum and that of the rectum which is greater than that of the sacral curvature. this curvature has been designed in order to form valves, known as Houston valve. It is not constructed with the rectal mucosa; but with the circular muscle of the rectum. There are three valves altogether in the rectal wall; two of them are situated on the left lateral wall and the third one on the right side of the rectum (Fig. 1.3).
Nevertheless, the physiological role of the rectum being placed under the peritoneum is to enhance the propagative movement of the feces in one direction, but the physiological function of the Houston valves has not been fully defined in the literature.
3
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Fig. 1.3: The rectum in sagittal section, displaying the Houston valves
It seems it acts as a shelf, upon which the lumps of solid feces are stuck up, one after another, thus protecting the lower rectum from being overloaded and distended. At the same time, the anal sphincters are spared from being subjected to a constant gravitational pressure that could have imposed downwards by the solid feces.
It also permits the flatus, passing through the space that is maintained between the rectal wall and contralateral Houston valves. If these valves were not existing in the rectal wall, the lower rectum and the anal canal would have been packed with the solid feces that would not permit the flatus to get through the anal orifice. Its physiological function in the defecation of the feces will be described later.
 
FUNCTION OF THE COLON
The average volume of the liquid, known as chimes, passing through the large gut would be around 300 – 500 ml. And they are isotonic. This volume eventually transforms into solid feces, by the time it arrives into the rectum. It is related to the duration of the transit time and related to total length of the gut.
The main function of the colon is to absorb water, electrolytes, and certain vitamins and possibly amino acids, but it does not absorb carbohydrates, fats, proteins and calcium. Most of the absorption of water and nutritional elements takes place along the right half of the colon, and left half of the colon acts as reservoir for the feces to be shifted down to the rectum at a suitable duration. Because of this functional difference, the blood supply to the right colon is also different and greater than that in the left colon.
In the past, the rectum used to be the usual site and route for infusion of saline and dextrose. Surprisingly, it does not induce transmission of bacteria into the circulatory system. Although it is much less traumatic and commonly used in the children, it is no longer in practice for various reasons. But this route is still used in the clinical practice for the absorption of drugs. These are antibiotics, narcotics, steroids and bronchodilators and it is often used in the treatment of ulcerative colitis and proctitis with other drugs, used as enema.
Nevertheless, the functional state of the colon plays an important part in maintaining the body fluid and nutrition that depends upon the total transport time from the pylorus to the sigmoid colon. According to literature, the transport time from the pylorus to the ileocecal valve is 6 hours, and it is 12 hours between the ileocecal valve and the sigmoid colon. This function could be affected adversely by other diseases. They are food poison, cholera, salmonella typhoid, ulcerative colitis, Crohn's ileitis and colitis or intraperitoneal abscess. Inflammation of mucosa, or inflammation surrounding the intestine may delay the absorption of the fluid or it may cause increased secretion of fluid from the inflamed or ulcerated mucosal wall that leads to rapid transit of motion, often referred to as bouts of intestinal hurry.
Loose motion may occur, if the functional state of the colon is interfered with, by shortening of the transit time for the feces. This may result from the partial resection of the colon or bypass procedure—thus shortening its transit length and time, or it could be interfered with, by the advanced diseases causing communication between the colon and small intestine or between the colon and the stomach. These conditions are referred to as fistula.
Colon has no somatic nerves supply. Hence, it does not elicit pain when its wall is cut with cutting diathermy needle, but it has a parasympathetic and sympathetic nerve supply, known as Auerbach's myenteric plexus that maintains the peristaltic movement. Apart from these neural plexus, the movement of the gut, known as peristalsis is also initiated by the tone of the muscles. The peristalsis has two components of movements. One is segmentation, that helps needing and mixing up the intestinal contents; and other one is propagative movement that assists in moving the contents forwards.
Evidence of bowel sounds on auscultation through the abdominal wall suggests turbulence of gas and water. This is due to the effect of two peristaltic movements of the gut, but passage of flatus through the anus is mainly the result of propagative peristalsis. It implies that the continuity of the lumen or passage of the gut and functional state of the neural plexus has recovered. Absence of flatus suggests that there is either mechanical obstruction or paralytic ileus. The latter could be associated with peritonitis, or with the hypokalemia.
Again, the peritonitis may result from inflammation, infection or injury to the peritoneum. Hence, bowel sounds 4and flatus remain silent in all these conditions. In all postoperative cases, bowel sounds return sooner than the passage of flatus. The reasons for the delay in the passage of flatus are associated with the edema and inflammation around the site of the anastomosis. It takes four to five days to settle the edema around the site of anastomosis, to restore the continuity through the gut anastomosis and to return the functional state of the neural plexus. Oral feeding should not be commenced until the patient has admitted that flatus has passed per rectum.
The functional movement of the gut, known as gut motility is judged by the frequency of defecation per day. Mass movement of the semisolid feces is initiated by the combination of intrinsic neural innervations and tone of the colonic muscles. Hence, volume is one of the important factors, causing local distention of both circular and longitudinal fibers of the colon. Overdistention may cause atony of the muscles. Constipation is the result of either lack of local stimulation of the tone of the gut wall or due to atony of the gut wall.
In dehydration, colon tends to absorb fluid from the feces, thus reducing its volume into round dry balls, often referred to as pellets. As a result, lots of dry hard feces are necessary to induce the tone of the colon, but pellets of feces delay the initiation of the local tonicity of the circular muscles of the colon. Hence, bulky feces is the main factor for maintaining the tone of the muscles and transit time, from the cecum to the rectum. Average time for the test meal is around 6 hours from the stomach to the cecum and another 6-12 hours are required for the motion to pass from the cecum to the rectum, but the transport time is much slower in the rectum.
 
APPLIED ANATOMY AND PHYSIOLOGY IN THE MECHANISM FOR DEFECATION
The ampulla of the rectum is a storing house for both wind and feces. it has Houston's valves incorporated with the rectal wall. These valves keep holding the lumps of feces on its shelf, thus delaying its descent and at the same time protecting the anal orifice from being subjected to overloading with the feces. This delay may allow the small round feces like pellet to be held up in the ampulla of the rectum, until they build up the pressure, causing distention of the rectal wall.
The circular muscles of the rectum such as Houston's valves keep on squeezing and pushing the feces downwards, concurrently and sequentially. This peristaltic action is carried out by contraction of the circular muscles and the Houston's valves of the rectum.
As a result, the puborectalis muscles and the distal rectum are forced to be stretched up by those lumps of feces. Its purpose is to accommodate more lumps of feces, forming a continuous sausage-shaped or pipe stem type of feces in most cases.
When the distention of the rectal wall and the puborectalis muscles exceeds its limit, the stretch receptors present in the rectal wall and the puborectalis muscles are triggered off in order to induce reflex action that conveys the inhibitory effect on the tone of the sphincteric muscles. This inhibitory reflex that is mediated through the spinal cord, produces relaxation of muscle, thus allowing the anal canal to be distended by those feces and air. In sequence, the propagating peristalsis sets in propelling, the lumps of feces further downwards through the anal canal— thus exerting pressure upon the anal sphincters and the anal orifice. The consequent effect would be a gentle awareness for defecation. All these actions lead to progressive discomfort around the perineum.
In some cases, defecation could be held back by squeezing the anal sphincters for some time, until a suitable time and/ or place is available, but eventually the desire for defecation is triggered off, once the puborectalis muscles exceeds their limit of stretch. The consequent effect would be squeezing the rectal wall forcing the feces further down. It would act like squeezing the toothpaste tube. At that moment of time, a constant discomfort around the perineum is experienced because of the fact that feces are trapped within the anal canal, by the contraction of the puborectalis muscles at the upper end and closure of the anal orifice at the distal end of the feces.
The circular sphincteric muscles surrounding the impacted anal canal are subjected to rhythmic contraction. This may generate discomfort through the perineal muscles. And eventually, it would not be possible any longer in holding the defecation back.
While sitting on the commode, the longitudinal muscles of the rectum play an important part in opening the anal orifice. In normal condition, anal canal and anal orifice remain closed at rest by the tone of the sphincteric muscles. It opens up passively by a combination of descent of the feces and by inhibitory reflex action, resulting from the distention of the rectal wall and the puborectalis muscles. The loss of muscle tone of the anal sphincters allows opening of the anal orifice, thus propelling the bulk of the feces down through the anal orifice. It is assisted by raising the intraabdominal pressure, which is maintained by the contraction of the abdominal muscles and by holding the inspiration. During this process of defecation, the longitudinal muscle of the anal canal keeps pulling the anal sphincters upwards or holding them in situ, while the feces continue moving slowly down, out of the anal orifice concurrently.
As a result, the descent of the feces is accelerated by the combined contraction of the abdominal muscles, circular muscles of the rectum and the puborectalis muscles; all of which exert together, squeezing the feces concurrently, until the bolus of the feces pushes down through the anal orifice, where the 5circular muscles of the subcutaneous external anal sphincters are stretched passively in pari passu with the delivery of the feces, like delivery of a baby through the cervix uteri. All the anal skin covering the anal verge is stretched and rolled out when the bulky motion is coming out slowly.
The final act of defecation is completed by the contraction of the subcutaneous external anal sphincter; but the latter will only work after the feces being expelled out of the anal orifice. This contraction is the result of return of the muscle tone of the external anal sphincters, and it acts like a wiper of the bottom; but its action is repeated at the end of each spell, until the defecation is completed, while sitting on the commode.
However, the defecation is a complex physiological action regulated by the spinal reflex action, and operated by the combination of the rectum, puborectalis muscles, and anal sphincters. Puborectalis muscle is a U-shaped sling that remains attached across the lateral and posterior wall of the rectum and its fibers pass across the longitudinal fibers of the rectum and keep holding the rectum angulated forwards at the level of anorectal ring (Figs 1.2 and 1.4). It is striated muscle and a part of the levator ani muscle. Therefore, the position of the rectum that is held angulated forward at the level of anorectal ring is regarded to be another break to the descent and defecation of the feces.
This muscle that lies above the upper border of the deep external anal sphincter is stretched by the distention of the rectal wall. Hence, the Levator ani muscles are also affected by such distention. The puborectalis muscle holds the key for the urge defecation and keeps holding the feces back, thus protecting the anal sphincters from its continuous sphincteric action.
Previous study suggested that the pressure of the anal canal was found reduced, when the rectal wall was distended by inserting a balloon into the rectum. And the authors claimed in their study that this loss of pressure was evident despite paralyzing the external anal sphincters.5, 6 Their inference was that this change in pressure of the anal canal was attributable to relaxation of the internal anal sphincter. Such conclusion was not consistent with the function of the anal sphincters.
In all instances, the anal canal remains closed not by voluntary action of the anal sphincters, but by the muscles tone of the external anal sphincters. These muscles are striated muscles and ten times thicker than that of internal sphincter. Hence, these muscles keep the anal canal closed by the muscle tone. Of course, paralysis of these striated muscles would obviously lose its muscles tone and would lose the intraluminal pressure of the anal canal. In contrast, the internal anal sphincter is composed of smooth muscles, similar to that of the rectum. Hence the above inference, derived from their studies was not consistent with the facts.
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Fig. 1.4: The one of the U-shaped sling of the puborectalis muscles to be divided by the scissors
Nevertheless, further study confirmed that dilatation of the rectum by the balloon showed inhibition of the electrical response in the external anal sphincters and the levator ani muscles.7 In another study, incontinence was reported in the results of sphincter saving low anterior resection of the rectum, where most of the rectum was removed at the operation.8
Despite all these conflicting reports, the fact has to be recognized that volume of the stool mass seems to be the primary factor for rectal dilatation. This induces urge defecation that is mediated via the spinal reflex neural action. The latter is triggered off through the stretch receptors present in the rectal wall, and puborectalis muscle. Therefore, the urge to defecate will not be initiated until the rectal wall and the puborectalis muscles exceed their limit of distention that depends upon the volume of the feces present in the rectum or anal canal.
In the literature, it has been postulated that this reflex action is initiated by the distention of the ampulla of the rectum, it is debatable whether the defecation is initiated by the distention of the rectal wall or by the puborectalis muscles or by a combination of both muscles. It is more likely that the urge to defecate is induced by the effect of stretch receptors present in the rectal wall and puborectalis muscles. Obviously, these receptors are stimulated by the distention of the rectum and puborectalis muscles.
Furthermore, this will also affect the levator ani muscles that continue resisting the intraabdominal pressure during defecation. At the same time, it will keep holding the sphincters steadily in places against the downwards forces of the feces. Furthermore, puborectalis muscles, levator ani muscles and external anal sphincters are innervated by the same pudendal nerves (S2, S3 and S4). It seems more likely that the reflex action for urge defecation is mediated through these neural flexus, supplying to those muscles.6
The circular muscles of the external anal sphincters are striated muscles; they keep the anal canal closed by its muscle tone alone and have no power to keep the anal canal open, unless these muscles are relaxed by voluntary action. The same mechanism plays in the subcutaneous external anal sphincter, which also has no physiological power to open the anal orifice voluntarily; but they have a power to defer the defecation that is carried out by just squeezing the anal orifice voluntarily. This voluntary action keeps the orifice closed further tight. This is due to the fact that they are not attached to the levator ani or anococcygeal raphe.
When the subcutaneous anal sphincter squeezes voluntarily, the anal orifice is closed and drawn inwards and upwards. As a result, the longitudinal muscle of the rectum, being a smooth muscle goes into spontaneous retraction. Ano-coccygeal raphe that lies between the coccyx and the external anal sphincters does not participate in defecation but it supports the pelvic floor and keeps holding the anus in place during defecation.
 
DISEASES OF THE COLON
Colonic diseases remain silent for many months, until it interferes with its physiological functions. These are loss of appetite, dehydration, malnutrition, weakness or feeling of discomfort in the belly or having abnormal bowel movements. For the ordinary people, it is not easy to recognize the abnormal symptoms that may develop slowly. Patients may anticipate that something in their belly is not right but they do not know exactly the reasons for being unwell or whether something serious has been growing in their belly. The symptoms that persist over many weeks are usually referred to as chronic and in other cases; the symptoms that appear abruptly without prior warning are referred to as acute condition that needs urgent attention of medical care.
Before discussing the individual medical problems, trainee surgeons need to understand the function of the gut. The whole length of the intestine has been anatomically divided into small and large intestine. Again the latter is subdivided into colon, rectum and anus.
 
PATHOLOGICAL LESIONS OF THE COLON
Colonic diseases could be classified in the following groups:
  1. Benign tumor.
  2. Malignant tumor.
  3. Inflammatory disease.
  4. Other benign lesions.
  1. Benign Tumors
    a. Benign epithelial tumor
    -
    Adenoma
    Villous papilloma
    Familial polyposis.
    b. Other varieties
    -
    Lipoma
    Leiomyoma
    Neurofibroma
    Hemangioma.
    c. Hamartomas
    -
    Juvenile polyp
    Polyps of Peutz-Jeghers syndrome.
  2. Malignant Tumor
    -
    Mainly adenocarcinoma
    Carcinoid syndrome.
  3. Inflammatory Diseases
    -
    Ulcerative colitis
    Crohn's colitis
    Diverticulitis
    Amebic colitis
    Benign lymphoma.
  4. Other Benign lesions
    -
    Hyperplastic or metaplastic mucosal polyps
    Pneumatosis cystoids intestinalis
    Hypertrophied anal polyp or papillae.
 
CLINICAL IMPORTANCE OF BENIGN COLONIC LESIONS
 
A Broad Presentation of Polyps or Papilloma
Although this pathological lesion is simple to understand, it is often misunderstood and is neglected, because of rare clinical presentation. First of all, it arises from the epithelium of the colonic mucosa and remains initially as a tiny and localized growth in any part of the colon or rectum. It grows slowly and becomes either sessile without a stalk or large with a stalk. It has various names. These are polyp, adenoma, familial polyp, adenomatous polyp, and villous adenoma or villous polyps. One needs to understand the difference between the polyp and the adenoma. The latter, contrary to polyp contains the glands arising from the mucosa. Although it is a benign lesion, it may change to malignant condition later in life.
 
CHARACTERISTIC FEATURES OF A POLYP
The normal color of the colonic mucosa is pale, but the adenomatous polyp would appear to be pink or red color, because of increased vascularity.
In most instances, adenoma or papilloma remains symptoms-free. Nevertheless, they may present with bleeding, discharge of mucus, diarrhea and tenesmus. It may prolapse through the anus; if it is located in the lower rectum and has a long pedicle. It may present as anemia or as intussusception or recurrent spasm in the abdomen. The etiology of anemia could be attributable to chronic blood loss from its surface. In most instances, they are identified during investigations for other conditions.7
These investigations are rectal digital examination, rigid or flexible sigmoidoscopy and colonoscopy or double-contrast barium enema. These investigations are carried out for routine cancer screening program, constipation, and change in bowel habit or bleeding per rectum or anemia.
These lesions are also suspected in routine radiological investigation such as double-contrast barium enema, which may suggest a localized filling defect, whether or not it was a lump of feces or colonic lesion. This suspicious looking lesion needs to be confirmed by colonoscopy or by flexible sigmoidoscopy that depends upon the site of the lesion, shown on the barium enema films. In most cases, the report turns out to be no pathological lesion in the colon, provided the colonoscopy has been carried out with a good bowel preparation.
 
EPIDEMIOLOGICAL AND PATHOLOGICAL FEATURES
The adenoma is used to be regarded as premalignant lesion. It is often present, concomitant with the malignant growth and the commonest site for adenoma is in the sigmoid colon and the rectum. Its incidence varies between 2 to 8 percent. It may present with various shapes and sizes, ranging from a split pea to a small cherry or plum. It could be sessile or pedunculated. The pedunculated lesion moves around within the lumen of the colon and could be of mushroom like appearance. The length of the pedicle varies between half an inch and one and a half inch.
Most adenoma has a smooth or mildly lobulated mucosal covering and its color is similar to the surrounding colonic or rectal mucosa, but it could be pink or red. All lesions must be removed for tissue diagnosis and to exclude malignancy. Further review should be done in every six months with a view to checking whether it has recurred. it is also possible that a separate lesion may be identified in the same anatomical region.
 
BROAD OUTLINE OF TREATMENT
If the lesion is pedunculated or sessile and located within the reach of the rigid sigmoidoscope, it could be removed by a long biopsy forceps through the rigid sigmoidoscope. The procedure is more often done while having the rectal examination in the outpatient clinic. No bowel preparation or sedation is necessary, but patient must be explained about the merits of the treatment and the procedure involved.
If the lesion is located beyond the reach of the rigid sigmoidoscope, then patient should be brought back for flexible or colonoscopy or is referred to the colleague for such procedure being carried out. It is also possible to carry out the same procedure at the end of the clinic, if there is such facility available for performing the flexible sigmoidoscopy to be carried out in the outpatient clinic.
 
POLYPECTOMY THROUGH THE COLONOSCOPE
Before considering for colonoscopy, it is important to document other medical conditions which could prevent the procedure for colonoscopy. These are:
Recent myocardial infarction in less than 6 weeks—This procedure may cause cardiac arrhythmias. Other contraindications are acute or chronic ulcerative colitis and crohn's colitis, diverticulitis, ischemic colitis, postradiation proctitis. These cases remain at greater risk of perforation of the gut due to inflammation of the bowel.
Polypectomy must not be done, if the patient is on anticoagulant therapy, or on aspirin.
Patient must be explained again about the complication and procedure, before a written consent is obtained. Rectal wash-out is normally given a few minutes before procedure being undertaken in the colonoscopic theater, the treatment is by snaring of the polyp either through the colonoscope or flexible sigmoidoscopy (70-110 cm). Two types of colonoscopes are available. One is longer ranging from 165 to 180 cm. This is suitable for the examination of the cecum. Durability of this type of colonoscope is short due to the fact that its wires may breakdown due to manipulation. The shorter one is between 130 cm and 140 cm.
Performance of the colonoscopy depends upon the cooperation of the patient and experience of the colonoscopist. It is advisable to carry out this procedure under short-acting intravenous sedation. The popular choice is midazolam. The recommended dose is between 2.5 mg and 5 mg. In addition, injection of pethidine 50 mg may be given either at the outset or later, if necessary. These drugs are given slowly. In some cases, injection of Buscopan 20-40 mg could be used, during the procedure.
In this procedure, the patient must have intravenous cannula onto the dorsal vein of the hand. Patient lies on the left lateral position with both knees onto brought towards the pelvis. First rectal digital examination should be carried out with right index finger, using a generous KY jelly. The end view of the colonoscope is first examined for sharpness of the focus, brightness of the light, air flow and suction apparatus, before it is gently inserted into the rectum by the right hand.
Generous lubrication is used all around the scope, every time it is pushed inside, under direct vision. It should not be pushed until the lumen of the gut is well-visualized with minimum air insufflations used. Overdistention of the gut may cause pain and discomfort and it may also cause angulation of the colon. To avoid this problem, air is again sucked out, after the scope has moved further forward.8
The procedure is repeated and the tip of the scope is manipulated around the bends or around the mucosal folds, until the lesion is recognized. At times, saline wash-out needs to be given through the side channel in order to clean the lens and to push the solid feces out of the field of vision. If the patient is in distress, it could be due to overdistention of the belly, short-acting sedation and buscopan could be given through the cannula. Alternatively, all air could be sucked out by a combination of manipulation of instrument over the lower abdomen along with the suction of air and feces. Both procedures could be done concurrently.
Patient must have electrode pad attached to the thigh or on the buttock, in case the polyp needs to be snared by electrocoagulation. The power setting should be around 35-50W. If the size of the stalk of the polyp is greater than 1cm, power setting should be increased in order to coagulate the vessels running through the thick-walled part of the stalk.
Having identified the polyp, a long flexible snare loop connected to diathermy electrode is passed through the side channel of the instrument, until the snare loop is seen protruding out of the plastic tube. Once the lesion is recognized, the loop of the snare is manipulated to be pushed around the pedicle and the snare is slowly withdrawn towards the end of the plastic tube, until the pedicle is snugly caught within the loop.
The plastic tube is pushed down and away from the scope and under vision, while the diathermy-peddle is touched by the foot. This allows cauterization and severance of the polyp.
In case the snaring has failed despite using the higher power setting, then following items need to be checked, whether the complete circuit has been maintained and whether the electropad has been placed under the buttock or across the thigh, whether the snare has been placed properly around the stalk and connected to the electrocoagulation circuit.
When the polyp has been snared successfully, the snare is pulled out and biopsy forceps is next passed through the same side channel in order to grasp the said detached polyp. If it has been picked up by the forceps, the scope is slowly withdrawn along the biopsy forceps that keep holding the polyp.
If the polyp appears to be sessile, it could be removed with a long flexible biopsy forceps passed through the side channel of the telescope. Any remnant, left in situ, is cauterized with coagulation diathermy. The tissue is sent for histology. It does not cause great deal of complication for this procedure.
 
COMPLICATIONS OF THE PROCEDURE
First, there could be a false passage of the colon due to a faulty technique, poor visibility and poor bowel preparation. Mucosal trauma may be possible due to lack of experience in handling the instrument, or by reversing the tip of the colonoscope, forming an inverted U loop, within the lumen of the rectum.
The immediate complication is perforation, and bleeding from the site of operation. The lesion may be lost in the lumen. In this case, colonoscopy is withdrawn slowly, while looking for the tumor. Alternative procedure is to give a rectal wash-out on the same table and the patient is asked to open the bowel in a bedpan, where the resected specimen is discharged with the motion. It is then retrieved from the pan. Alternatively, patient is admitted in the ward for a bedpan in which the specimen may drop.
If the patient complains of pain in lower abdomen and appears to be in a state of shock, patient needs to be admitted straightaway for urgent resuscitation. In a state of hemorrhagic shock, patient will appear pale looking, sweating and there would be low blood pressure and rapid pulse rate. The first medical care is to start resuscitation with intravenous infusion of colloids and blood, sedation and antibiotics. Blood transfusion should be considered, if the hemoglobin is less than 10 gm/dl.
Once the patient has recovered from the shock, examination of the abdomen is carried out, whether or not there is any evidence of peritonitis and paralytic ileus. Both rectal digital and sigmoidoscopy are carried out, if possible. In most cases, bleeding stops but for persisting bleeding, the bleeding points may require to be controlled by a gentle touch with electrocoagulation under general anesthesia and on the operating table.
Later, a plain x-ray of abdomen in both erect and supine position is taken. This may reveal any gas under the diaphragm or around the colon. If the diagnosis is in doubt, water-soluble contrast known as gastrograffin enema should be carried out. Once the diagnosis has been confirmed, emergency laparotomy should be carried out for the repair of perforation and for the construction of a transverse-loop colostomy.
In other cases, secondary hemorrhage may occur after two weeks. It occurs when the necrotic tissue tends to be dislodged from the site of electrocoagulation. Patient may collapse in the bathroom at home. For a mild type of bleeding that may be noticed along with the defecation, no more special care is necessary, but blood hemoglobin should be checked, before prescribing iron tablets to the patient.
 
CLINICAL FEATURES AND TREATMENT OF VILLOUS PAPILLOMA
A villous papilloma is another variety of adenoma, usually develops in the rectum. It has shaggy surface with characteristic frond-like appearances and ill-defined edges. It has a wider base, covering a large area, but it is mobile. In most instances, they are located in the posterior wall of the rectum. It discharges jelly-like mucoid material and thick watery motion that contains high-rich potassium.9
Patient may be dehydrated with electrolyte abnormality in which hypokalemia would be the major concern to the surgeon. Histologically, it is regarded to be benign but malignant change may occur unless dysplastic changes are noticed on histological examination.
All those patients, usually above the age of 30, are investigated in order to exclude any other pathological lesion present in the colon. These include, sigmoidoscopy, ultrasound scan of the liver, kidneys and abdomen, contrast barium enema, and blood tests for electrolytes and full blood count, blood sugar. After reviewing all these results, colonoscopy should be arranged in order to complete the investigation.
Patient needs to be admitted for correction of dehydration and electrolytes imbalance with the supplementation of potassium, either in the infusion or orally. Preoperative bowel preparation is carried out with oral laxative and rectal phosphate enema followed by rectal saline wash-out; before the patient is operated upon. A full discussion should be held with the patient, for obtaining consent for the operation. Patient must be informed that the tumor needs to be resected locally. And there remains further possibility for developing a local recurrence. It is also important to draw his attention that malignant change may be noticed in the resected tumor or it may develop later that depends upon the local treatment and the report of the histology.
The treatment entails a fulguration of the tumor with a ball pointed electrode or a wide submucosal resection of the tumor under direct vision. This depends upon the size and location of the tumor.
 
Operative Procedure
Under general anesthesia, patient is put on the lithotomy position. Sterile drapes are put around the perineum and legs. Rectal digital examination is done in order to palpate the tumor about its size and mobility. Rigid sigmoidoscopy is also carried out in order to see the rectum and a part of the sigmoid colon, whether there is any other additional growth located higher up.
Anal orifice is dilated with 2-3 fingers. A self-retaining retractor with two blades is inserted through the anus. And it is held in position by retracting the two blades in situ.
The proximal edge of the tumor is grabbed with a Babcock forceps. It is gently brought down in order to define the edge of the attachment of the tumor with the rectal mucosa. Assessment is made whether the defect of the submucosal space could be covered technically with the mobilization of the surrounding rectal mucosa after resection of the tumor is carried out with a cutting diathermy needle. This assessment is done by pulling the tumor down, measuring its size and by evaluating the mobility of healthy mucosa, around the base of the tumor; before the resection is contemplated.
After this assessment, a stay suture is inserted a little above the upper edge of the tumor. A few more Babcock forceps are applied to the edge of the tumor in order to act as traction, during the process of cutting the tumor edge, using an angled diathermy needle. Submucosal resection of the tumor is continued from the proximal side, and at the same time the surrounding cut edge of the mucosa is mobilized to be stitched together. This bridging across the defect is made by a continuous suture. The procedure is continued downwards until the whole tumor is resected out. During resection, bleeding points are stopped with diathermy forceps. At the conclusion, the retractors are removed. The wound is covered with jelly net. The specimen is sent for histology.
 
Postoperative Care
Patient should be kept nil by mouth for a few days, until flatus has passed. Once bowel has moved, patient is allowed home, but is reviewed six weeks later.
Alternative to submucosal resection is the resection of the tumor with a special form of resectoscope, through an operating sigmoidoscope, like TURP. Other approach is to destroy the surface of the papilloma by diathermy; but total ablation of the tumor is not possible in this procedure. There are many disadvantages in undertaking this procedure. However, patient may experience with wet bottom and foul smell due to discharge of mucous, soiling the under-pants or dress.
Every six weeks, the patient is reviewed at the outpatient clinic and further surgical intervention may be necessary within 3-6 months time. The condition is not curable but it requires regular surveillance.
If the villous tumor is located in the sigmoid colon or in the rectum, laparotomy is necessary for resection of the gut that depends upon the location and histological grade of the tumor.
 
CRITERIA FOR CONSIDERING MALIGNANCY IN THE BENIGN ADENOMA OR VILLOUS PAPILLOMA
  1. Age: If the polyp develops in a young child, it is known as juvenile polyp, and is regarded to be benign but if it occurs in the older age group, the lesion could be either of the pathology.
  2. A family history should be obtained in order to exclude familial polyposis coli. They are treated like malignancy.
  3. Histology report is not 100 percent reliable. Negative report does not exclude malignance. It is more likely to happen that biopsy was taken from the non-malignant site of the adenoma.
    10
  4. Characteristic appearance of the growth—Malignancy should be suspected, if the surface is ulcerated or the growth appears to be large in size and indurated.
 
DIFFERENCE BETWEEN THE ADENOMA AND VILLOUS PAPILLOMA
The incidence of adenoma is reported to be 84.6 percent and that of villous papilloma 11.6 percent. And the average size of the former is between 2 and 7 cm and that of the latter ranges from a few mm to 9 cm. Majority of the adenoma is pedunculated but villous papilloma is sessile in almost 90 percent of the cases, or finger like projection and rarely pedunculated. And they are almost solitary compared to the adenomatous lesions. The commonest anatomical sites for the adenoma remain in the sigmoid colon but the villous papilloma develops by contrast in the rectum more frequently than in the sigmoid colon.
 
FAMILIAL POLYPOSIS
Familial polyposis is an autosomal dominant condition. The name familial polyposis implies that it is hereditary and genetic disease, transmitted by the father to the offspring in both sexes, but only half of the children are likely to inherit the disease and the affected member will pass the gene to the next generation. The average age for the development of symptoms is 20 and it takes 10-15 years to develop cancer in these polyps. It is diffusely present in the large bowel, right down to the anal canal. It is more in numbers in the left side, but they are generally uniformly distributed between the cecum and anal canal. They are adenoma and are of various sizes. Eventually, malignancy develops in these adenomas.
 
CLINICAL PRESENTATION
In early life, they remain silent, but with the age, the symptoms are presented initially with a slight soft motion, that may progress to increased number of frequency. In most cases, either the parent or the child may not pay much attention to the unusual symptoms, until it becomes evident that bowel movements are getting worse and associated with frank diarrhea, discharge of mucus and blood in the motion.
These cases are often presented with multiple sebaceous cysts, dermoid cysts, bony exostoses. If the patient is presented with multiple soft and hard tissue tumors, while attending the clinics, suspicion should arise and further investigation should be contemplated to exclude familial polyposis of colon. Suspicion should also arise in the investigation of ulcerative colitis among the younger patients.
In the routine examination, rectal digital examination would reveal the features of adenomatous polyps. Sigmoidoscopy will show multiple polyps and normal looking mucosa in the intervening space. In contrast, the findings would be quite different in the case of proctocolitis, in which, there would be no classical vascular pattern in the rectal mucosa, and there would be contact bleeding associated with pus and blood in the lumen.
Other investigations include colonoscopy and double-contrast barium enema. It is also important to remember how to differentiate the distinct features between the ulcerative colitis and the familial intestinal polyposis in barium enema. In the former case, the barium enema will show contraction, and lack of haustration.
 
CHOICES OF TREATMENT MODALITIES
It is a difficult situation in which surgeons could not predict the prognosis for any conservative surgical procedures used in dealing with this case. If total colectomy followed by ileorectal anastomosis is carried out, patient needs to be followed up every three months that includes check sigmoidoscopy. This would be expensive and would render psychological trauma. As a result, patient would be tied down to a particular medical team or a hospital.
Again, there remains a further risk of multiple operative procedures. In these cases, tissue diagnosis is first done by biopsy and then fulguration of the recurrent polyps is done, if the histology report suggests benign lesion. And eventually abdominoperineal resection of the rectum is undertaken for the recurrence of malignant tumor in the rectal stump or anal canal. Again, this procedure would be much more difficult because of previous operative adhesions developed in the pelvis or in the abdomen.
Therefore, considering the morbidity and financial implication, it is safer to do total panproctocolectomy and terminal ileostomy, before the age of 30 or when the disease has reached to a period of 10 years, and when the symptoms have developed. The only problem remains with the young patients whether they are prepared to accept the burden of permanent ileostomy and to sacrifice the enjoyments of family or married life. Regrettably there is no satisfactory alternative choice in the safe treatment for this inherited disease.
Postoperative complication following total colectomy or panproctocolectomy or AP resection has been described in the respective chapter. It is especially important to add one import complication associated with this disease. There remains a risk of developing desmoids tumor in the abdominal scar.
 
DIFFERENCE BETWEEN ADENOMA, PEUTZ-JEGHERS SYNDROME AND FAMILIAL POLYPOSIS
Polyps also develop in other parts of the alimentary tract, but it is associated with pigmentation in the skin and buccal 11mucosa. It is a benign clinical condition and a hereditary condition.
The commonest site for developing polyp is in the jejunum but it can occur in other parts of the small intestine. the pigmentation usually appears to be irregular flakes over the lips and commonly in the mucocutaneous junction of the lower lip, buccal mucosa and over the plates, but not on the tongue, fingers and toes.
Polyp could be of various sizes and similar in appearance to other adenomas or familial polyposis, but not associated with buccal or lips pigmentation. Nevertheless, it presents confusion when these polyps develop intussusception or bleeding or recurrent episodes of pain in upper abdomen. Investigation is necessary to establish the differential diagnosis and to establish the causes of symptoms. Surgical intervention is only indicated if they pose persistent problems not resolving spontaneously.
 
OTHER BENIGN POLYP IN THE COLON, RECTUM AND ANUS
 
Lymphoma
This benign tumor remains silent in most cases and is diagnosed incidentally during routine rectal examination. It appears like any other polyp. Although a polyp found on proctoscopy or sigmoidoscopy in the rectum, may be innocent or benign pathology, thorough clinical history and investigation is necessary. It should be removed for tissue diagnosis. If the histology report suggests that the tissue removed from the rectum is lymphoma, no further treatment is necessary and complete excision is not important, because of the fact that it does not change into lymphosarcoma.
 
Lipoma
Lipoma is a lobulated and capsulated fatty benign tumor. It can develop in any part of the body, but it is rarely found in the alimentary tract. If it is present in the gut, commonest site would be in the cecum, but it can develop in other sites of the colon and rectum. In most cases, it remains symptoms-free, but it may cause intussusception in the cecum and it may cause some discomfort. It lies in the submucosal layer and unlikely in the subserous layer. This fatty lump may be palpable on abdominal examination.
Differential diagnosis may be difficult, if barium enema shows a filling defect in the wall of the cecum or colon. Because of the radiological finding, further investigation should be arranged. These are ultrasound scan, CT scan, MRI scan and colonoscopy. Conservative line of approach may be recommended, if the colonoscopy confirms no evidence of mucosal growth, but laparotomy should be considered because of symptoms of pain, and obstructive features. Although lipoma is a benign tumor, it cannot be certain of its pathology without histological examination. In this scenario, one should not ignore the radiological or CT scan report.
 
Leiomyoma
Leiomyoma is also a rare variety and a benign tumor, but it may change to malignancy, presenting as leiomyosarcoma. It develops usually in the smooth muscle layer of the gut.
It can affect both sexes and at any age. Its size and consistency varies. When it is small in size, it would appear to be rubbery and firm but when it is large, it could be lobulated. It may project through the overlying mucosa into the lumen, causing discomfort and partial obstruction. It may also project through the serosal wall into the peritoneal cavity. Those tumors develop in the intramural part of the colon, are not capsulated, but others in the rectum may have a capsule. It may ulcerate through the mucosa, causing bleeding.
This rare tumor is diagnosed at the laparotomy or through the sigmoidoscopy. Total excision will protect the patient from any risk of malignant change. Hence, histology report will guide the surgeon whether or not it has been excised completely.
Other rare variety of pathological lesions present in the colon or rectum is Hemangioma. If they are encountered in any clinical examination, conservative line of approach should be observed. In any condition of acute hemorrhage, the lesion needs to be excised along with a segment of bowel. Coagulation diathermy or sclerosing injection into the vessels would be ineffective in most instances.
 
PAPILLOMA OF THE ANUS
Papilloma may develop around the anus. It may be associated with penile or vaginal warts. Its etiology is not known, but viral in origin has been referred to the literature. Poor local hygiene and anal sexual intercourse are the alternative cause for these benign conditions. It could be transmitted to sexual partner.
They are multiple and may develop into the lower part of the anal canal. It causes discomfort and produces foul odor. Differential diagnosis has to be made between the condyloma latum due to syphilis and squamous cell carcinoma. In the latter case, induration is a distinct feature around the lesions and tissue diagnosis is done while dealing with this lesion.
Treatment is the recurrent fulguration or a partial excision like hemorrhoidectomy. Specimen must be sent for histology following each surgical treatment.12
REFERENCES
  1. Heald RJ, Husband EM, Ryall RD. The mesorectum in rectal cancer surgery: the clue to pelvic recurrence? Br J Surg 1982; 69:613–16.
  1. Textbook of Gray's Anatomy, 37th Edition, 1989.
  1. Last RJ. Anatomy Regional and Applied, 4th edition, J and A Churchill Ltd:  London,  1966.
  1. Saha SK. Critical evaluation of dissection of the perineum in synchronous combined abdominoperineal excision of the rectum. Surgery Gynecology and Obstetrics. 1984; 158:33–38.
  1. Denny-Brown D, Robertson EG. An investigation of the nervous control of defecation. Brain 1935; 58:256.
  1. Duthie HL, Watts JM. Contribution of the external anal sphincter to the pressure zone in the anal canal. Gut 1965; 6:64.
  1. Porter NH. Megacolon: A physiological study. Proc Roy Soc Med 1961; 54:1043.
  1. Parks AG, Porter NH, Melzak J. Experimental study of the reflex mechanism controlling the muscles of the pelvic floor. Dis Colon and Rectum 1962; 5:407.