Acute gastrointestinal bleeding due to penetration of a partially thrombosed hepatic artery aneurysm into the duodenal bulb is rare but has been reported. Ultrasound, computed tomography, and angiography are the methods of choice for aneurysm detection. If clinical review and endoscopy are inconclusive in determining the cause of upper gastrointestinal bleeding, and no usual diagnosis can be established, a search for arteriointestinal fistula must be initiated.