Mucosal changes in the large bowel with endometriosis: a possible cause of misdiagnosis of colitis?

Endometriotic deposits are not uncommon in the large bowel of women. Because the symptoms produced by endometriosis may lead to investigation by colorectal endoscopic biopsy, the aims of this study were to assess the range of mucosal abnormalities that may occur and to determine whether this could represent a significant potential diagnostic problem. We found mucosal changes in eight of 10 cases of colorectal endometriosis; however, the abnormalities (ulceration, gland architectural disturbance, crypt abscess formation, increased inflammatory cell presence, and smooth muscle fibers between glands in the mucosa) were focal and directly related to endometrial deposits. In one case an abnormal colonic biopsy specimen from a patient with endometriosis supported the erroneous clinical diagnosis of Crohn's disease. Comparing a group of women with endometriosis to a group with adenomyosis of the uterus showed that although more women with endometriosis have endoscopic large bowel biopsies, there was no significant excess of biopsy specimens showing inflammatory changes. Our conclusion is that the endometriosis of the large bowel can masquerade as inflammatory bowel disease or ischemic changes and the possibility should be borne in mind, particularly in cases with atypical clinical features or very focal histological changes.