Microvascular abnormalities in the mucosal prolapse syndrome.

Twenty two cases of colorectal mucosal prolapse from a variety of clinical situations were examined histologically to identify changes in the microvasculature which may predispose to ulceration. The findings were compared with 10 tubular adenomas and 10 hyperplastic polyps. Fibrin insudation into vessel walls and thickened mucosal vessels were significantly associated with the presence of ulceration. Possible mechanisms of ulceration are discussed, and an hypothesis based on a microvascular pathogenesis is presented.