Importance of Hyperplastic Polyps and Adenomas 5mm or Less in Diameter That Are Detected by Screening Flexible Sigmoidoscopy

Abstract

Background: The need for full colonoscopy in patients with hyperplastic polyps or adenomas 5mm or less in diameter that are detected by screening flexible sigmoidoscopy (FS) is controversial. The aim of this study was to determine the prevalence of proximal colonic neoplasms in a large cohort of patients with distal polyps detected by screening FS. Methods: Consecutive asymptomatic patients at average-risk for colorectal cancer who were referred for screening FS were prospectively enrolled from 1/98 through 10/03. A detailed medical history was obtained from all patients prior to FS, and colonoscopy was offered to all subjects with polyps on FS. Polyps detected by FS were classified as hyperplastic, diminutive adenomas (≤ 5mm in diameter), small adenomas (6 - 9 mm in diameter), large adenomas (≥ 10mm in diameter), or cancers. In patients with more than one polyp, classification was based on the most advanced lesion. For each type of lesion on FS, we determined the proportion of patients who had any adenomas, advanced colonic neoplasms, or cancers detected by colonoscopy in the proximal colon. Advanced colonic neoplasms were defined as adenomas ≥ 10mm in diameter or any adenoma, regardless of size, with villous histology, high-grade dysplasia, or cancer. Results: A total of 2,084 patients (mean age 66.5 ± 9.4 years) were enrolled, and the mean depth of insertion of the sigmoidoscope was 57.7 ± 7.1 cm. One or more polyps were detected in 491 of the 2,084 patients (23.6%), and the most advanced lesion on FS was classified as a hyperplastic polyp in 8.4% of patients, adenoma ≤ 5mm in 6.4%, adenoma 6 - 9 mm in 3.2%, adenoma ≥ 10mm in 3.2%, and cancer in 0.5% of subjects. Of the 491 patients with a polyp on FS, 482 of these subjects (98.2%) underwent colonoscopy and 97.5% of these examinations were complete to the cecum. Conclusions: There was a substantial prevalence of proximal adenomas and advanced colonic neoplasms in asymptomatic average-risk patients with distal hyperplastic polyps and adenomas ≤ 5mm in diameter. Colonoscopy should be offered to individuals found to have hyperplastic or diminutive adenomas on FS.