Secondary Aortoduodenal Fistula Diagnosed after Repeated Gastrointestinal Bleeding Episodes in a Patient With Prior Aortic Graft Surgery.

Secondary aortoduodenal fistula (sADF) is a rare but life-threatening complication after aortic graft surgery. Diagnosis is often challenging, particularly when contrast-enhanced computed tomography (CT) and endoscopy results are inconclusive. We report a case in which diagnosis was challenging due to contrast media allergy and non-diagnostic endoscopic findings, highlighting the importance of clinical suspicion in such scenarios. A 76-year-old man with a history of graft replacement for a ruptured abdominal aortic aneurysm presented with five episodes of gastrointestinal bleeding over 3 months. Despite multiple examinations, no bleeding source was identified. Eventually, after the patient developed hypovolemic shock, contrast-enhanced CT was performed with informed consent, which revealed contrast extravasation from the aorta into the horizontal portion of the duodenum. Endoscopy subsequently identified an exposed vessel in the same location, confirming the diagnosis of sADF. Endovascular aortic repair was successfully performed. This case underscores the need to consider sADF in patients with aortic grafts who present with recurrent, unexplained gastrointestinal bleeding.