Gastrointestinal tract involvement by gynecologic diseases.

Involvement of the gastrointestinal tract by gynecologic disease processes-endometriosis, gynecologic neoplasms, inflammatory processes, and complications from radiation therapy or surgery for gynecologic tumors-may mimic primary gastrointestinal carcinoma on radiologic images. Endometriosis most often involves the anterior wall of the rectosigmoid colon, adjacent to the pouch of Douglas, and typically produces extrinsic mass effect on the serosa, with the overlying mucosa left intact. Direct extension of ovarian cancer to the colon through the subperitoneal space produces mass effect with serosal spiculation, tethering, and fixation; annular constriction; or partial or complete obstruction. Intraperitoneal seeding of ovarian carcinoma most frequently involves the colon and is seen as extrinsic masses, often with serosal spiculation and tethering. Cervical carcinoma, which most commonly spreads by direct invasion of the pelvic side wall and adjacent structures, produces serosal spiculation and circumferential narrowing. Benign ovarian or uterine tumors are purely extrinsic and have a smooth interface with the colonic wall. Tubo-ovarian abscesses are difficult to differentiate from cystic ovarian neoplasms or endometriomas. Radiation colitis causes narrowing of the rectum with intact mucosa and can be differentiated from recurrent tumor, unlike radiation-induced injury of the small bowel, which may be difficult to distinguish. Surgical adhesions produce a discrete transition point between dilated bowel proximally and nondilated distal bowel. Familiarity with the varied patterns of gastrointestinal tract involvement is important for accurate interpretation of imaging studies.