Primary aortoenteric fistula.

Primary aortoenteric fistula is a rare complication of aortic aneurysms. This cause of gastrointestinal bleeding poses significant diagnostic challenges due to its nonspecific presentation. We report a case of an 80-year-old man with right flank pain and rectal bleeding. The patient had been admitted 2 weeks before with the same symptoms. Upper and lower endoscopies were unremarkable, but abdominal computed tomography scan showed evidence of aortoduodenal fistula. An emergency laparotomy with aortic bypass and fistula closure was performed and the patient was able to recover in the following weeks. This case highlights the need for a high index of suspicion to avoid diagnostic delay that frequently has fatal results.