We present the case of a 66-yr-old woman who was admitted to a surgical intensive care unit with life-threatening rectal bleeding. Despite the use of angiography and repeated computed tomography scans, the diagnosis of a primary aortoduodenal fistula secondary to an abdominal aortic aneurysm was not made, leading to a delay in diagnosis until the time of surgery. The reliability of radiological investigations and the importance of being alert to the possibility of this extremely rare condition are discussed.

Implications: We describe the delayed diagnosis of an aortoduodenal fistula related to an abdominal aortic aneurysm. We emphasize that computed tomography scan results may be unreliable for detecting this pathology in patients who are hemodynamically unstable.