Preparation of the colon for flexible sigmoidoscopy and colonoscopy

Abstract

The clean colon! A subject which, despite its mundane connotations is, nevertheless, demanding more attention from the colonoscopist and the radiologist who require a clean colon before performing a proper examination. The colonoscopist, I believe, is more persevering in achieving this objective if for no more reason than esthetics-for who likes to tunnel through feces? The subject of laxative action is also receiving the attention of our best gastrointestinal physiologists. 1 • It is now appreciated that most laxatives produce a secretory diarrhea, acting through the cyclic AMP system and other lesswell-understood mechanisms, paralleling in many ways pathologic diarrheal states. Hopefully, in the future, with a better understanding of laxative actions, we might more intelligently approach the problem of colon cleansing. Dr. Rosco Miller estimates that about 1.4 million barium enemas are performed yearly in the United States. The number of these exams which require repeated studies at tremendous cost in money and time is not known. However, in his department, 50% of patients had repeated barium enemas because of unclean colons. With proper colon cleansing that figure dropped to 2%. I am not aware of how many colonoscopies or sigmoidoscopies are being performed yearly and how many are inadequate because of poor preparation. Nevertheless, with a good technique, a clean colon can be achieved for the vast majority of examinations. The need for proper examination of the colon is emphasized by the fact that increased survival in patients with colorectal cancer is correlated with early detection of the malignancy. McCallum suggested that insofar as 70% of large bowel cancer will be located in the distal 50 cm of the bowel, a procedure by which one could routinely visualize this area would offer great potential for the detection of cancer. After reviewing more than 40,000 cases of colorectal carcinoma reported to the Connecticut Tumor Registry over a period of 33 years (1940-1973), Snyder et al. reported that the proportion of colorectal cancer occurring above the rectosigmoid junction has been increasing over time. These investigators suggested that only about half the colorectal cancers can now be detected with the rigid sigmoidoscope, and other tests must be used for the diagnosis of the increased numbers of cancer in the upper part of the colon. The flexible sigmoidoscope is now being evaluated as a method of detection of this latter group, and its role in the future as a diagnostic and therapeutic instrument is not clear. Preparation for a total colon examination requires more effort than for a limited colon examination performed by sigmoidoscopy. Therefore, 2 methods will be described. Published evaluations of X-Prep liquid for a variety of radiographic procedures prompted consideration for its merits for colonoscopic examination. 13