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Sigmoidoscopy: from the inside out.


The American Cancer Society predicts that more than 150,000 new cases of colorectal cancer will occur in the next year with more than 60,000 deaths, making the disease this nation's second-leading cause of cancer death. Almost all of these cases will arise from previously benign polyps (small intestinal tract growths) that could have been removed before becoming malignant, had they been detected early enough.

One sign of bowel cancer is blood in the stool, but visible bleeding occurs only after the cancer has become well-established. However, bleeding can be detected at a much earlier stage (invisible, or "occult," blood) with the use of "Hemoccult" slides. Small samples of stool are collected and smeared on these specially prepared cardboard slides before being mailed to a laboratory for testing--a simple and inexpensive procedure. Further diagnostic tests to identify the source of the blood are then required if the test is positive. If polyps or any cancerous lesions are found, they are removed.

A negative Hemoccult test does not, however, rule out the possibility of premalignant polyps. Thus, the thorough general medical checkup that everyone should have from time to time should include the somewhat uncomfortable procedure known as sigmoidoscopy. The most commonly used instrument is the rigid sigmoidoscope, a metal instrument about 10 inches long that can view the interior of the rectum and the lower colon. Although rigid sigmoidoscopy is safe and effective for detecting polyps and other lesions within reach of the instrument, it cannot detect those further up in the colon. At the same time, researchers have found that the older the patient, the more likely such lesions are found in those more distant regions.

To determine the frequency of cancerous and precancerous lesions in persons with no bowel disease symptoms, the Indiana University Medical Center in Indianapolis is conducting an extensive study on volunteers in the 50- to 75-year age range who are undergoing colonoscopy, a procedure that employs a state-of-the-art instrument known as the flexible sigmoidoscope. Almost three times the length of the rigid sigmoidoscope, the flexible sigmoidoscope can be passed through the entire length of the large bowel, enabling both the operator and the patient to view every square inch of one's colon in glorious living color through a tiny TV camera in its tip. (Your editor, having recently volunteered himself for the procedure, can report that, although perhaps not as exciting as "Knots Landing," the drama that unfolded before him was one of the best he has seen, the test having been passed with "flying colors," so to speak.) Of the first 210 Indiana subjects studied, 53 were found to have one or more polyps, and 2 had cancer. Both cancers and all of the larger polyps were found in persons 60 years of age or older. More than half of the polyps and one of the cancers were in parts of the colon well beyond reach of normal sigmoidoscopy.

Considering that none of the 210 subjects had any bowel symptoms or bowel disease history, and that all had negative Hemoccult tests, the results are impressive indeed. Unfortunately, the procedure is not without risk, to both the bowel and the pocketbook. Even in the hands of a highly trained gastroenterologist, bowel perforation may occur (albeit rarely), necessitating immediate emergency surgery. Therefore, colonoscopy is not something to be performed in a doctor's office. More importantly, the cost is upwards of $300. Although the procedure may not soon become routine in all periodic medical examinations, in selected cases it has enormous diagnostic value.
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Publication:Medical Update
Date:Nov 1, 1990
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