Prolapse of the large intestinal mucosa occurs in various situations including at the margin of a colostomy, the apex of hemorrhoids protruding outside the anus, and in the context of diverticular disease. However the best known sites of mucosal prolapse are the anterior wall of the rectum where it gives rise to the solitary ulcer syndrome and the anorectal junction resulting in a peculiar polyp called “cloacogenic polyp.” These are both benign conditions. Common clinical symptoms are constipation and/or red blood loss per annum. The endoscopy of the solitary ulcer can show a variable picture of erythema, a shallow ulcer, or even a polypoïd lesion. The histology is characteristic. The mucosa around the solitary ulcer shows crypt distortion, reactive epithelial cells, and typical fibromuscular obliteration of the lamina propria. Inflammation is usually mild. A “cloacogenic polyp” appears as a villiform tumor mass at the anorectal junction and has a great potential to be confused with other polyps such as adenomas or even carcinoma. It is important to recognize these lesions in order to avoid the morbidity and mortality associated with major surgery (misdiagnosis of neoplasia) or the side effects of long-term medical treatment.
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