Aortoenteric Fistula: A Rare Cause of Gastrointestinal Bleed Requiring Emergent Surgical Intervention

Abstract

Introduction Aortoenteric fistula is a rare life-threatening diagnosis that may initially present as a minor gastrointestinal bleed, but will inevitably become a surgical emergency. This case highlights the need for a high clinical index of suspicion of aortoenteric fistulas in patients with a history of prior aortic surgery to avoid diagnostic delay, which is often fatal. Case A 81-year-old male with a past medical history significant for an abdominal aortic aneurysm repair and partial colon resection who presented to the Emergency Department complaining of bright red blood per rectum over the past 24 hours. Upon arrival, his blood pressure was 133/60, pulse 101, RR 18, temperature 97.7, and O2 saturation of 98% on room air. On physical exam, he had no abdominal tenderness. He was found to have a hemoglobin of 7.8 from a baseline of 10.2. The patient was started on pantoprazole and an emergent upper endoscopy was performed, which showed evidence of necrotic tissue in the D2 portion of the duodenum. Surgery was consulted. An emergent exploratory laparotomy was done, which revealed a fistula between the duodenum and the aorta. GI surgery mobilized the duodenal fistula by removing adhesions, and vascular surgery transected the aorta and removed the graft. The patient was stable after the excision of aorto-duodenal fistula and oversewing of the aorta. Discussion Aortoenteric fistulas (AEFs) are uncommonly encountered but are important to consider in the differential diagnosis of gastrointestinal bleeding in patients who have had prior aortic surgery. Primary AEFs arise de novo between the aorta and bowel, while secondary AEFs (SAEFs) are usually caused by prosthetic vascular grafts eroding into the intestine as in this patient. Pulsation of vascular grafts against the intestine may cause erosion of the duodenal wall, leading to hemorrhage. Any part of the gastrointestinal tract may be involved, but most commonly it is the third part of the duodenum. SAEFs may present as gastrointestinal bleeding and occasionally as sepsis. Patients initially have “herald bleeding” - intermittent episodes of bleeding due to thrombus formation -followed by massive hemorrhaging. A CT abdomen with contrast is the best diagnostic test if an AEF is suspected; AEFs may also be detected on endoscopy as in this patient. Emergency exploratory laparotomy is warranted immediately upon diagnosis, as mortality is 100% if not surgically treated.