In this day and age of potent, broad-spectrum antibiotics, we are seeing antibiotic colitis much more commonly. This disorder is due to Clostridium difficile mediated toxin and can occur with any antibiotic including any of the broad-spectrum, systemic or oral antibiotics. The Clostridium difficile toxin elaborates a cytotoxin which causes focal necrosis along with acute inflammatory exudate which is the pseudomembrane. The clinical illness is generally that of abdominal pain, cramping, watery diarrhea which occasionally becomes bloody in 5 - 10% of cases, fever, leukocytosis, and rebound tenderness. The characteristic appearance sigmoidoscopically is that of large confluent pseudomembranes which are often present along with erythema and edema, these pseudomembranes appearing as 1 - 5 mm yellow plaques with their size depending on the timing of colonoscopy in relation to the onset of diarrhea. These are generally smaller in the first 18 hours and generally enlarged after 72 hours into the illness where they may become up to 5 mm size. It is estimated that one third of cases have only mild rectal and sigmoid erythema and in a small percentage of cases, complete rectal sparing has been described. The finding of pseudomembranes in the context of recent antibiotic therapy and C. difficile toxin in rather characteristic and diagnostic of this disease which is important to recognize and treat aggressively since its morbidity and mortality are significant if undiagnosed.

The last type of inflammatory and miscellaneous colitis to be mentioned is that of ischemic colitis which is being recognized increasingly in the elderly patient who presents with lower abdominal pain and rectal bleeding. Generally, the incidence is highest in those patients with concomitant dehydration, cardiogenic shock or the presence of underlying atherosclerosis. The appearance sigmoidoscopically depends on the stage in which it is diagnosed, as in the first 72 hours the acute state of patchy hyperemia mucosa alternating with pale areas are through to result from transient blanching of the mucosal blood vessels. Over a 24 hour period the erythema coalesces and ischemia begins to spread to involve more mucosal area at which point superficial ulcers which are 2 - 4 mm in size occur. In the subacute stage which generally occurs three to seven days after the onset of symptoms, ulcers are found which are elongated and serpiginous (snake-like). These can often times be confused with Crohn's disease. In the chronic stage which generally occurs two weeks to three months after the onset of symptoms, residual granularity can occur and occasionally stricture formation. Rare types of colitis, radiation colitis, Behcet's disease, hemolytic ureic syndrome, malakoplakia, schistosomiasis, colonic tuberculosis, Yersinia enterocolitis cytomegalovirus and drug induced colitis are rare and are not worthy of lengthy discussion at this time.

Diverticular disease (a term which encompasses all stages; prediverticular phase, diverticulosis and diverticulitis), of the colon is a common occurrence in the aged. From 10 - 50% of persons over the age of 40 have diverticulosis coli. The figure rising each year with aging. The sigmoid colon is the most common area of the colon involved, however, any area of the colon can be involved. Diverticula are produced by herniation of the mucous membrane trough the bowel wall in response to high intramural pressure. Diverticular orifices can be recognized endoscopically when they are present associated with muscular hypertrophy, hypertonicity of the colon and spasm. Within the sigmoid they are recognized as 3 - 5 mm circular openings in the central portion of the short haustral segment situated between the enlarged valvulae. Colonic diverticula are often times an incidental finding. The importance to the endoscopist is that these can be easily confused with the lumen making the examiner reluctant to proceed. One often times cannot tell the opening to the diverticulum from the lumen opening which is often times smaller in the examiner have any doubt differentiating lumen versus diverticulum, the prudent measure is to withdraw the scope first and re-establish the general direction of the valvulae rather than to proceed blindly into what may be a larger diverticulum with the likely potential for perforation. In the case of diverticulitis, the area immediately around the diverticula becomes spastic, narrowed, with enlarged valvulae. Purulent material may often times be seen extruding from the mouth of the perforated diverticulum, although this is unusual. In diverticular strictures in late stage disease, one sees varying degrees of narrowing of the lumen which can often times be difficult to differentiate from neoplastic strictures. Often times this differentiation can only be made by appropriate biopsies of the segment, radiographic correlation and in certain percentage of cases, surgical intervention.

Colon polyps are perhaps the most common pathologic abnormalities found on sigmoidoscopic examination with an incidence approaching up to 50% of colons examined at the time of autopsy. Up to 30% of all patients with rectal bleeding will be found to have colonic polyps. In the case of a patient with one rectal polyp, a synchronous polyp found elsewhere in the colon may be expected in up to 50% of patients undergoing total colonoscopy. Colon polyps are classified in numerous ways. The epithelial types which can be either neoplastic or non-neoplastic. Neoplastic polyps including adenomas can be tubular, tubulovillous or villous, and polypoid carcinomas. Our discussion regarding the description of the most common polyps will include the above. Less common, rare polyp syndromes will be briefly mentioned, including multiple polyposis, Peutz-Jeghers disease, and other rare polyposis syndromes.
 
 

Adenomas are the most common type of polyp noted at sigmoidoscopy. 65% of these lesions are found between the splenic flexure and rectosigmoid junction. The most common location overall is the sigmoid followed by descending colon, followed by the rectum. The average size is between 5 mm and 2 cm and up to 35% of patients will have more than one. The appearance of a typical adenoma (tubular, tubulovillous or villous) varies depending on the size of the polyp. the tiny adenomas, less than 3 mm, appear as excresences which are somewhat redder than the surrounding mucosa. The small adenomas of 4 - 9 mm are smooth, often perfectly round, sessile, or pedunculated polyps. The moderate sized adenomas from 1 - 2 cms in size are often round but can be lobulated with erythematous mucosa and if stalks are present, thicker stalks than those of smaller adenomas. The larger adenomas of greater than 2 cm size are often times multilobulated with each lobe in excess of 0.5 mm, as if the polyp was made up of multiple small adenomas fused up to make on large polyp. The tubulovillous adenomas are generally 1 - 2 cm or larger and tend to be pedunculated and wider with shorter pedicles than tubular adenomas. The villous adenoma appears as a soft, sessile lesion with a surface consisting of multiple 3 - 6 mm nodules, projecting off the surface for several millimeters. They are generally large with a maximum dimension varying anywhere from 1 cm up to 8 cms, most often sessile and up to 50% incidence of malignancy.

The hyperplastic polyps are the most frequent polyps found in the large intestine. These typically are less than 5 mm size and have a characteristic endoscopic appearance of a small, sessile, smooth, pale lesion which blends in fairly imperceptibly with the surrounding mucosa. These can often be multiple and do not generally have neoplastic potential.

Juvenile polyps, as the name indicates, are most common amongst children and adolescents with the average age of 4 or 5 years but they are occasionally found in adults. The rectum and sigmoid are most common sites for occurrence and these polyps typically are less than 2 cm in size and are stalked and endoscopically often times appear beefy red, smooth and hemorrhagic appearing. Peutz-Jeghers is a rare polyposis syndrome consisting of GI polyps and pigmentation of the skin and/or mucous membrane transmitted as a mendelian dominant gene. These polyps often resemble adenomas which can vary in size.

Familial polyposis coli is another rare syndrome of hundreds and thousands of adenomas found in the rectosigmoid and remaining colon. This disorder is inherited as a mendelian dominant gene which is not sex-linked and is easily recognizable by a literal carpeting of the colon with small sized polyps varying in sizes and shapes. The high incidence of malignancy at an early age is well-known in this condition. Rare syndromes of Gardner's syndrome, Canada-Cronkhite syndrome and Turcot's syndrome will not be discussed in any detail at this time. Generally, the practitioner should document the presence of a polypoid lesion and make the appropriate referral to one who performs total colonoscopy to ultimately excise the polypoid lesion and look for additional ones.

Colorectal carcinomas are the most common gastrointestinal malignancies in industrialized countries with the exception of Japan where gastric carcinoma is the most common. These have much the same distribution as adenomas, most frequently situated in the distal colon and rectum (up to 75% of all lesions). Colorectal cancers have characteristic appearances so that endoscopic diagnosis is generally easy. If the scope is able to reach the lesion the diagnosis is made by biopsy and occasionally cytology increasing the diagnostic potential of the examination. The following are limitations of endoscopy:

1. It is often difficult to obtain an entire picture of the lesion, particularly in cases where there is high grade stenosis.

2. Bleeding may prevent observation.

3. Remaining stool may obscure the whole or part of the tumor.

4. Occasionally sigmoidoscopy can be hazardous in a situation where intestinal adhesions produced by the cancer are extensive.

Other neoplastic diseases involving the colon can be confused with primary colon cancer. Primary colon carcinoid which can occur in the rectum as a central, submucosal, umbilicated lesion, lymphosarcoma, and other secondary malignancies metastasizing to the colon such as that from the ovary, uterus, prostate, pancreas, gallbladder, appendix or other distant organs often can be confused with primary lesions. Those non-neoplastic lesions such as inflammatory disease involving neighboring organs of female genitalia, pancreas, kidney, can be confused with malignant disease and benign inflammatory bowel disease with associated stenosis, stricture or pseudopolyps are often indistinguishable endoscopically and can only be differentiated in the context of the clinical history and with appropriate histopathologic information. In general, a raised, ulcerated, cauliflower, or exophytic lesion should be biopsied, taking a small bite of tissue from the friable lesion itself, not near the area where it is attached to the bowel wall and not within an ulcer crater. Generally, cancer tissue is very hard and fragments off and does not require sharp biopsy, whereas normal tissue is elastic and easily movable. For distal rectal lesions, retroflexion of the sigmoidoscope is often times valuable for seeing very distal lesions which are not as clearly visible by direct vision. This maneuver is often times technically difficult and occasionally painful for patients, particularly with large bore endoscopes. Certainly, one must never forget the importance of a careful digital examination which, in most cases, detects up to 35% of malignancies and polyps.

Colonic appearances secondary to cathartics, melanosis coli and laxative colon, are seen in conditions where patients have been using laxatives in the class of anthraquinones which include Cascara, Senna, rhubarb, and other emodins where the active agent is hydroxylmethylanthraquinone. Other laxatives such as Phenolphthalein (Ex-Lax), Bisacodyl (Dulcolax), have also been implicated as a cause for cathartic colon but not melanosis coli. The appearance of melanosis coli is that of brown patches of streaks throughout the colon which appear to be interconnected in a reticulated pattern. In the cathartic colon, the principal involvement is in the right colon where the patulous ileocecal valve is noted and loss of haustration. Colonic ulcer syndromes, a solitary rectal ulcer syndrome (stercoral ulcer), this uncommon condition of solitary rectal ulcer can occur due to excessive straining, fecal stasis, bedridden states, where ischemic necrosis of the surface epithelium will occur and in the ulcer state, ulcers varying from 2 - 8 mms in size 5 - 10 cms from the anal verge are noted as discrete, punched out, well demarcated ulcers with raised, erythematous mucosa surrounding the edges.

Colitis cystic profunda - this non-neoplastic condition is possibly related to the solitary rectal ulcer syndrome and is rare and it appears that of single or multiple nodules which on biopsy have a rubbery consistency with slight erythematous overlying mucosa.

Pneumatosis coli - This is an unusual condition of the colon characterized by gas-filled cysts in the wall of the colon, often associated with other underlying diseases, i.e. chronic obstructive pulmonary disease, gastric cancer, peptic ulcer disease with obstruction. The appearance of these lesions are those of submucosal polypoid masses ranging from 2 - 3 mm in size which are soft and easily compressible, which on biopsy often pop or hiss as if air is being expelled and the cyst is seen to deflate.

Colonic anastamoses - The sigmoidoscopist needs to be aware of the range of appearances for an uncomplicated anastamosis and that of a recurrent neoplasm or inflammatory condition involving the anastomosis. A wide variation in the degree of nodularity and appearance of the folds may occur depending on the technique used by the surgeon, whether it be hand sutured or stapled. One may find suture granuloma, anastomotic stricture, or significant deformity secondary to unusual healing processes.

1. Watch the patient and assess his condition with every movement of the scope.

2. Once the procedure has begun do not move your eye from the eyepiece, viewing the interior of the colon constantly.

3. Always be alert to find out the center of the lumen & adjust the tip to it.

4. Do not bend the scope acutely while inserting it.

5. When advancing the scope recall the pathway it followed upon entering the colon and think of the shape of this pathway when further introducing the scope.

8. Remember that pain is a warning sign do not persist in any maneuvers that cause the patient pain.

9. Do the procedure as rapidly as possible to avoid irritation of the colon and patient.

10. Be aware of your own abilities and know when to stop the examination and withdraw the scope.