S3707 The Atypical Clinical Appearance of a Giant Colon Diverticulum: A Case Report

Introduction: Around 30% of Americans over 50 are affected by diverticulosis. Diverticula are outpouchings of the bowel wall prevalent in the digestive tract. Colonic diverticulosis is common, but giant colonic diverticulum (GCD), defined as >4 cm, is rare, with ≈200 reported cases. GCDs carry a high risk of serious complications, including perforation, obstruction, fistula formation, and hemorrhage. This case report reviews a patient with GCD concerning for colon cancer, whose workup was modified following a literature review. The patient subsequently underwent a successful laparoscopic robotic-assisted partial sigmoidectomy. Case Description/Methods: A 77-year-old man with a history of diverticulitis and sigmoid diverticulosis on a colonoscopy in 2023 presented with a 12-pound weight loss. On exam, the abdomen was soft and nontender. Computed tomography (CT) scan showed a large mid-anterior abdominal dilated gas-filled apparent mass measuring 9.2 × 8.2 × 9.2 cm, along the mesenteric side of the proximal sigmoid colon. The wall of the mass measured 0.7–0.8 cm. Given the lesion’s size, there was displacement of the adjacent small bowel loops. Nonspecific small locoregional mesenteric and left retroperitoneal lymph nodes were noted. This mass was concerning for a primary exophytic sigmoid colonic malignancy. The gastroenterologist felt colon cancer was unlikely as a malignant lesion, with a colonoscopy performed 2 years prior being unremarkable for any suspicious malignant lesions. The patient’s prior CT in 2023 revealed an apparent lesion measuring 7.4 × 7.3 × 7.0 cm. After a literature search, the clinician was concerned for GCD and referred the patient for surgery, given the high risk of perforation with a colonoscopy. The patient underwent sigmoid resection with a minimally invasive robotic approach, resulting in the successful resection of the GCD. Discussion: GCD is a rare complication of diverticulosis, and its presentation as a palpable abdominal mass is uncommon. In this case, pre-operative imaging was crucial in identifying the large gas-filled structure that could have been mistaken for a cancerous mass. Given the size of the GCD and risk of perforation and complications, a robotic partial sigmoid colectomy was performed. This case underscores the importance of familiarity with GCD to be considered in the differential diagnosis of patients with atypical abdominal masses. Partial sigmoidectomy and diverticulectomy remain the most effective approaches for managing GCD and preventing subsequent major complications.