IMPORTANCE OF ADENOMAS 5 MM OR LESS IN DIAMETER THAT ARE DETECTED BY SIGMOIDOSCOPY

Background The need for colonoscopy in patients with adenomas 5 mm or less in diameter that are detected by sigmoidoscopy is controversial. Methods We prospectively determined the prevalence of proximal colonic neoplasms in asymptomatic patients at average risk for colorectal can cer, each of whose index lesion on screening fiberoptic sigmoidoscopy was a benign adenoma. Polyps found on sigmoidoscopy underwent biopsy, and colonoscopy was recommended to all patients with neoplastic polyps . Rectosigmoid adenomas were classified as diminutive (less than or eq ual to 5 mm in diameter), small (6 to 10 mm in diameter), or large (gr eater than or equal to 11 mm in diameter). Results Of 3496 consecutive patients referred for sigmoidoscopy, 311 had neoplastic rectosigmoid polyps; 108 of these patients were excluded from the analysis because of a history of colonic neoplasia, symptoms, prior colonic evaluation, or incomplete follow-up data. The remaining 203 patients made up the study group, and all underwent colonoscopy. Neoplasms were found in th e proximal colon in 40 of 137 patients (29 percent) with diminutive in dex polyps, 15 of 52 patients (29 percent) with small index polyps, an d 8 of 14 patients (57 percent) with large index polyps. Advanced neop lasms (adenomas greater than or equal to 10 mm in diameter, adenomas w ith a villous component or moderate-to-severe dysplasia, carcinoma in situ, or frank carcinoma) were found in 8 patients (6 percent), 5 pati ents (10 percent), and 4 patients (29 percent), respectively. Two pati ents with diminutive index polyps had proximal carcinoma in situ, and two had proximal stage I carcinomas; one patient with a large index po lyp had proximal stage III carcinoma. Conclusions The substantial prev alence of proximal colonic neoplasms, including advanced lesions, in a symptomatic average-risk patients with rectosigmoid adenomas less than or equal to 5 mm in diameter warrants colonoscopy in these patients. (C)1997, Massachusetts Medical Society.