Endometriosis of the Colon Diagnosed by Endoscopic Ultrasound

Purpose: Introduction: Endometriosis of the colon is not rare, but the diagnosis can be challenging given the varied clinical presentation and tendency for mural rather than mucosal involvement. Preoperative diagnosis is essential, as some patients may respond to hormonal therapy and avoid surgery. We present a case of colonic endometriosis in which endoscopic ultrasound established a definitive diagnosis. Case: A 27-year-old female was referred for colonoscopy after reporting a 1-year history of intermittent hematochezia to her primary provider. Colonoscopy revealed focal narrowing of the rectosigmoid colon, precluding passage of the endoscope; the mucosa was edematous and friable but not ulcerated. An elongated mass was noted proximal to the stricture, but biopsies showed normal colonic mucosa. Subsequent consultation disclosed that her rectal bleeding was cyclical, beginning 4 days prior to menstruation and ending a day after. Bleeding was associated with pelvic pain which resolved after her menses, between which she had no hematochezia or pain. She had gradual lengthening of her menstrual cycles and developed recent anemia. She had a spontaneous pregnancy 8 years prior, but no further pregnancies despite ongoing unprotected intercourse. Her family history was notable for endometriosis and colon cancer, both in 2nd degree relatives. CT scan confirmed circumferential thickening of the rectosigmoid colon with luminal narrowing. Endoscopic ultrasound revealed a 16-cm subepithelial hypoechoic lesion of the submucosa and muscularis propria causing wall thickening to 17 mm. Tru-cut biopsies from the colonic wall confirmed endometriosis. Given her desire for sterility, she underwent a Robotic-assisted modified radical hysterectomy with bilateral salpingo-oophorectomy, and incisionless laparoscopic rectosigmoid resection with transvaginal colon extraction. Histopathology revealed endometriosis of the uterine serosa and ovaries; the rectosigmoid colon contained endometriosis forming multiple intramural masses, with luminal narrowing to 0.8 cm. Discussion: Endometriosis affects the intestinal tract in 15-37% of patients, most commonly involving the sigmoid colon. Intestinal involvement can produce abdominal pain, a palpable mass or obstruction; catamenial hematochezia is less frequent. Intestinal endometriosis typically involves the subserosa and muscularis propria; mucosal biopsies may be negative or non-diagnostic. While MRI is useful for staging pelvic endometriosis, endoscopic ultrasound has a role in establishing the diagnosis of intestinal involvement, given it allows for mural or extramural sampling of deepseated lesions, as in this case.