Congenital arteriovenous fistula with aneurysm formation of ulnar artery origin.

Naturally formed arteriovenous fistula (AVF) causing local vascular aneurysm dilatation in the forearm ulnar artery region is rare and is exceedingly uncommon in any age group. Presented is a case of AVF in the left ulnar artery of a 39-year-old man in whom there was no history of trauma; the deformity had been noted since childhood. The AVF had become tortuous and enlarged in size as the patient aged. As a result, aneurysm dilatation formed on the base of the AVF and that of the ulnar artery origin. Despite normal preoperative Allen test result and normal preoperative finger pressure measurement with ulnar artery occlusion, arterial duplex imaging showed that the radial artery was the dominant artery of the left arm; the AVF was resected and the base of the aneurismal dilatation, which was directly related to the ulnar artery, was repaired for the sake of the natural continuity of ulnar blood flow.