S1769 Deeply Infiltrating Endometriosis Masquerading as a Sigmoid Adenoma

Introduction: Deeply Infiltrating Endometriosis (DIE) is defined as implantation of endometrial tissue outside of the uterus at least 5 mm beneath the peritoneum. While anywhere between 3.8-37% of patients with endometriosis may have bowel involvement, infiltration of endometrial tissue into the bowel mucosa is quite rare.1 In a systematic review of patients who underwent bowel resection for endometriosis, the mucosa was involved in only 6.4%.2 We present the case of a patient who underwent colonoscopy for rectal bleeding ultimately found to be due to intraluminal endometriosis of the sigmoid colon. Case Description/Methods: A 43-year-old female with a history of endometriosis and prior sigmoid polypectomy presented for surveillance colonoscopy in the setting of bright red blood per rectum and a known sigmoid adenoma. Colonoscopy revealed a scar in the sigmoid colon overlaid with residual polypoid tissue (Figure 1). Eleview was used to raise the lesion and piecemeal mucosal resection was performed using a snare. Following resection and retrieval of tissue, three hemostatic clips were successfully placed and the patient was discharged home without complications. Immunohistochemical analysis revealed glandular cells strongly and diffusely positive for estrogen receptor (ER) and paired-box gene 8 (PAX-8), suggestive of endometrium. There were numerous areas of intestinal tissue highlighted by the CDX2 marker interspersed with stromal cells positive for ER and neprilysin, which together confirmed the diagnosis of endometriosis with intestinal metaplasia. Discussion: Intraluminal colonic endometriosis is a rare form of DIE that may present as abdominal pain and rectal bleeding in the pre-menopausal patient. While colonoscopy may help visualize the mass, it is nearly impossible to distinguish endometrial tissue from intestinal metaplasia, and definitive diagnosis requires positive immunohistochemical staining. While symptoms may be mitigated with estrogen-progestin contraceptives and nonsteroidal anti-inflammatory drugs, curative measures have historically involved rectosigmoid resection.Figure 1.: CT abdomen/pelvis done on presentation demonstrated a large left-sided hernia with sigmoid colon in the hernia without otherwise any evidence of stranding, inflammation or obstruction. The right side was also noted to have a large hernia with what appeared to be the cecum and appendix in the hernia sac with stranding and some pericolonic fluid collection.