Flexible sigmoidoscopy as a screening test for colorectal cancer.

Flexible sigmoidoscopy (FS) is one of the screening modalities for colorectal cancer. The rationale for screening with flexible sigmoidoscopy is that it provides direct visualisation of the colon, and suspicious lesions can be biopsied. The most obvious disadvantage is that it examines only the lower third of the colon. The technical aspects of FS are sufficiently clear to enable us to define what FS can and cannot do. From the point of view of screening, FS clearly cannot completely exclude the presence of colon cancer in all asymptomatic people. A distinction must be made between screening the general population and testing the individual seeking screening. For the former, obtaining the greatest mortality benefit safely and at an acceptable cost to the nation is the crux of the matter. Recently published data indicate that FS is a cost-effective screening strategy, although colonoscopy and annual fecal occult blood test avert a greater number of cancer deaths. The results of randomised controlled trials of screening FS and colonoscopy, currently being conducted, will allow us to make a more accurate comparison with the established data regarding fecal occult blood test. In conclusion, flexible sigmoidoscopy every 5 years with or without FOBT is one of the screening methods recommended by major professional organizations. It identifies 50 to 70% of the advanced neoplasms, if any discovery of a distal neoplasia is followed up with a total examination of the colon by colonoscopy.