S3916 A Rare Cause of Rectal Bleeding: Inferior Mesenteric Vein Varices in a Non-Cirrhotic Patient

Introduction: Varices are a common cause of GI bleeding predominantly found in the gastroesophageal (GE) region and develop due to portal hypertension (PHTN) in the setting of cirrhosis. Rarely, varices may be found ectopically in small bowel, colon and rectum. Ectopic varices (EV) pose a diagnostic challenge due to anatomic location and elusive underlying etiology. We present a rare case of lower GI bleeding due to inferior mesenteric vein (IMV) varices in a non-cirrhotic patient. Case Description/Methods: An 84-year-old-man with history of coronary artery disease, abdominal aortic aneurysm s/p endovascular repair presented with rectal bleeding. Patient was hemodynamically stable. Labs showed a low Hb of 12.8. Colonoscopy showed mild pan diverticulosis and significantly enlarged veins noted at 50 cm around the splenic flexure. CT abdomen and pelvis with IV contrast showed superior mesenteric vein (SMV) collaterals and varices along the transverse and descending colon which drained into splenic flexure vein. This drained into proximal portion of the IMV which then drained into the splenic vein and not directly into inferior vena cava (IVC). This caused congestion in left colonic venous drainage and variceal formation. Liver was normal, no imaging or clinical evidence of cirrhosis or PHTN. Discussion: EV are defined as dilated portosystemic veins located in sites other than the GE area. While there's a paucity of data, about 17% of EV are found in duodenum, 14% in colon. and 8% in rectum. Most cases of EV are due to PHTN, congenital anomalous portosystemic anastomosis or related to thrombosis. EV may present with hematemesis, rectal bleeding, hematuria, or hemobilia. Endoscopic evaluation with esophagogastroduodenoscopy and/or colonoscopy should be pursued. Intravenous contrast enhanced computed tomography, double balloon or push enteroscopy and video capsule endoscopy may be considered. If EV are amenable to endoscopic intervention, then endoscopic band ligation and injection sclerotherapy can be used. Our case highlights a unique clinical scenario wherein IMV varices developed due to a rare congenital anomaly-left colonic venous system draining into splenic flexure vein which subsequently drains into IMV instead of the normal drainage pattern that entails SMV joining splenic vein to form the portal vein which eventually drains into IVC. This anomalous drainage pattern results in severe congestion in left colonic venous drainage with resultant IMV varices. Variable and complex manifestations such as our case warrant a high index of clinical suspicion in order to promptly diagnose and treat EV.