COLONOSCOPY - A REVIEW OF ITS YIELD FOR CANCERS AND ADENOMAS BY INDICATION

Colonoscopy for bleeding indications (positive fecal occult blood test , emergent or nonemergent rectal bleeding, melena with a negative uppe r endoscopy and iron deficiency anemia) has a substantial yield for ca ncers (1 per 9 to 13 colonoscopies), although slide rehydration of fec al occult blood tests decreases the yield (1 per 45 colonoscopies). Pr ospective studies indicate that nonbleeding colonic symptoms have a su bstantially lower yield for cancer than bleeding symptoms (1 per 109 c olonoscopies). Patients with indications for screening colonoscopy wit h a relatively high yield of cancer are those with Lynch syndrome (1 p er 39 colonoscopies) and males more than 60 yr old (1 per 64 colonosco pies). Perioperative colonoscopy in persons undergoing colorectal canc er resection has a high yield for synchronous cancer (2-3%). An initia l examination in persons with long-standing ulcerative colitis has a h igh yield for cancer (12%). Surveillance colonoscopy after cancer rese ction has an intermediate yield for anastomotic cancer (1 per 74 proce dures) and metachronous cancers (1 per 82 colonoscopies), although thi s number may overestimate the yield of metachronous cancer. Postpolype ctomy surveillance and ulcerative colitis surveillance colonoscopy hav e relatively low yields for cancer (1 per 317 and 360 colonoscopies, r espectively). However, postpolypectomy surveillance colonoscopy, in co mbination with initial clearing colonoscopy, has been proven to be alm ost entirely effective in preventing colorectal cancer death. Further, cancer yields for postpolypectomy surveillance should improve with im plementation of new surveillance guidelines, with little or no impact on mortality. The effectiveness of ulcerative colitis surveillance is less certain. Referral of patients with low-grade dysplasia for colect omy would improve the value and effectiveness of surveillance colonosc opy in ulcerative colitis. Adenoma yields at colonoscopy are relativel y independent of indication, as evidenced by the high yield of adenoma s in screening colonoscopy studies. Demographic factors, including inc reasing age and male gender, are important predictors of adenomas at i nitial colonoscopy. Age, male gender, and multiple and large adenomas at initial examination are predictors of adenomas at subsequent postpo lypectomy surveillance. Persons with ureterosigmoidostomies can be scr eened by interval flexible sigmoidoscopy and do not require screening colonoscopy. A history of breast cancer does not predict an improved y ield of colonoscopic screening compared to average-risk persons.