Primary aortoduodenal fistula: a unique presentation of a pseudoaneurysm associated with cystic medial necrosis.

A 42-yr-old man who exsanguinated from an acute upper gastrointestinal bleed was found to have a primary aortoduodenal fistula on postmortem examination. The fistula arose in an aortic pseudoaneurysm associated with cystic medial necrosis. Although there was no suggestion of Marfan's syndrome on physical examination, there was cystic medial necrosis of not only the involved aorta, but also other systemic arteries. Primary aortoduodenal fistula is a rare cause of acute upper gastrointestinal bleeding and is usually associated with atherosclerotic disease of the aorta. This is the first report of a pseudoaneurysm associated with cystic medial necrosis presenting as an aortoduodenal fistula.