Distal colonic neoplasms predict proximal neoplasia in average-risk, asymptomatic subjects

Flexible sigmoidoscopy has been recommended as a screening method to reduce the incidence of colorectal cancer in asymptomatic, average-risk subjects through the early detection and removal of polyps. However, the association between distal and proximal colonic neoplasia and, hence, the requirement for colonoscopic follow up of screen-detected distal neoplasms is unclear. Our aims were: (i) to evaluate the risk of having proximal neoplasms in tho se with distal colonic neoplasms; and (ii) to determine whether the risk wa s dependent on the number, size, histology or morphology of the distal lesi ons. We prospectively evaluated asymptomatic subjects in a flexible sigmoid oscopy based screening programme. Those with rectosigmoid neoplasia underwe nt colonoscopy. The number, size, histology and morphology of the polyps we re recorded. Advanced lesions were defined as adenomas > 1 cm or with a vil lous component or severe dysplasia, carcinoma in situ or cancer. Adenomatou s polyps were found in 17% (135) of screening flexible sigmoidoscopies. At colonoscopy, up to 30% of subjects with distal colonic neoplasms had synchr onous proximal lesions at colonoscopy and up to 20% had advanced proximal l esions. The risk of proximal colonic neoplasia was increased in those with distal sessile colonic neoplasms but appeared independent of distal lesion size, number or morphology. In conclusion, distal colonic neoplasia predict s proximal neoplasia in up to 30% of subjects and these were advanced lesio ns in up to 20%. We recommend that all subjects with biopsy proven distal c olonic neoplasia undergo colonoscopy.