NEW YORK, July 20 (Praxis Press) Whether or not colonoscopy is useful in screening asymptomatic adults for colorectal cancer is unclear. To determine the prevalence and risk of colonic neoplasia in asymptomatic patients, Lieberman and colleagues performed colonoscopy on 3 121 patients at 13 Veterans Affairs medical centers (see paper). Examination detected one or more neoplastic lesions in 37.5% of the patients, an adenoma with a diameter of at least 10 mm or a villous adenoma in 7.9%, an adenoma with high-grade dysplasia in 1.6%, and invasive cancer in 1%. They also found that patients with large or small adenomas in the distal colon were more likely to have advanced proximal neoplasia than were patients with no distal adenomas and that colonoscopy detects advanced colonic neoplasms that may be missed using sigmoidoscopy. Colonoscopic screening can detect advanced colonic neoplasms in asymptomatic adults that would be missed by...