A Large Sigmoid Mass Mimicking Colon Cancer in a Pregnant Female

Purpose: A 36 year old, gravida 3, para 0020 pregnant female presented to the emergency department with crampy abdominal pain and constipation. An ultrasound demonstrated an intrauterine pregnancy and a complex left adnexal cystic mass. MRI revealed a multicystic left adnexal mass and an 8 cm soft signal into the distal sigmoid, suspicious for an infiltrative mural lesion. The patient underwent flexible sigmoidoscopy which revealed a 7 cm polypoid, non-obstructing mass in the distal sigmoid, 18 cm from the anal verge. Biopsies revealed endometriosis without neoplasia. The patient was counseled and elected to continue her pregnancy. She developed preeclampsia, but otherwise underwent an uneventful caesarian section at 39 weeks. Endometriosis is a common diagnosis, affecting 15% of premenopausal women. The gastrointestinal tract is the most frequently involved site of extrapelvic disease, seen in 37% of patients with endometriosis. Of these patients, the rectum and sigmoid are the most commonly involved areas. Blood per rectum during menstruation is the most common presenting symptom. Frequently, cyclical abdominal pain and altered bowel habits are present. In rare instances, obstruction and even perforation can occur. Diagnosis is difficult, typically requiring laparoscopy or endoscopy with biopsy for definitive diagnosis. Mucosal involvement is uncommon. Furthermore, endometriosis appearing as a large focal colonic mass is rare. Treatment of intestinal endometriosis can range from a strategy of watchful waiting to hormonal treatment to surgery or resection.Figure: Sigmoid mass on MRI.Figure: Sigmoid mass on endoscopy.