Risk Factors of Advanced Adenoma in Small and Diminutive Colorectal Polyp

The aims of this study were to review the clinicopathological characteristics of diminutive (≤ 5 mm) and small polyps (> 5 mm but < 10 mm) and to evaluate the risk factors of advanced adenoma for polyps of diameter < 10 mm in the colon. The medical records of 4,711 patients who underwent first colonoscopy at outpatient clinics or health promotion center were reviewed retrospectively. We analyzed the presence and risk factors of advanced adenoma, which was defined as a villous or tubulovillous polyp, high-grade dysplasia or intramucosal carcinoma histologically. Total 5,058 polyps were detected in the 4,711 patients, and 93.0% (4,704/5,058) polyps were < 10 mm in size. Among them, advanced adenoma was noted in 0.6% (28/4,704) with a villous component in 19, high-grade dysplasia in 3, and adenocarcinoma in 6. Advanced and non-advanced adenomas differed significantly in age group, gender, and polyp size. Multivariate analysis showed that an advanced age (> 65 years), a male gender, and a polyp size of > 5 mm were risk factors of advanced adenoma. The incidence of advanced adenoma in polyps of < 10 mm was 0.6%. Polyp size, male gender, and age of > 65 years are independent risk factors of advanced adenoma.