Distribution of colorectal adenomas: implications for bowel cancer screening

Objective: To determine the distribution of colorectal adenomas relative to the splenic flexure in an asymptomatic population undergoing colonoscopy, as an indicator of the number of patients with adenomas who would be missed by screening with flexible sigmoidoscopy, Design: Retrospective survey of medical records. Setting: Private endoscopy centres in Melbourne, Victoria. Subjects: All 1131 asymptomatic individuals who underwent full colonoscopy between 1 January 1995 and 31 December 1997 after referral from a bowel can cer prevention program organised by the endoscopy centres. People referred were aged either 40 years or over with a first-degree relative with bowel c ancer, or 50 years or over with marked anxiety about bowel cancer. Main outcome measures: Presence and distribution of colorectal adenomas. Results: Polyps were found in 270 individuals (24%) and were confirmed to b e adenomas in 138 (12%). These 138 comprised 106 men and 32 women, with mea n age 54 years (range, 40-78 years). Most (86%) had a single adenoma, Posit ion of adenomas in relation to the splenic flexure was: distal only in 85 o f the 138 people (62%), proximal only in 34 (25%), and both distal and prox imal in 19(14%). Conclusions: In 25% of asymptomatic people found to have adenomas by this b owel cancer prevention program, the adenomas were found only in the proxima l colon, well beyond the reach of the flexible sigmoidoscope, This distribu tion of adenomas suggests that screening programs cannot rely solely on fle xible sigmoidoscopy.