Ruptured hepatic artery aneurysm in a domestic yak.

A 19.5-y-old, male domestic yak ( Bos grunniens) with a history of sudden unexpected death was submitted for autopsy. The yak had hemoabdomen, and a large blood clot was attached to the liver and forestomachs. The hepatic artery had a saccular aneurysm with a 1-cm tear. The arterial wall at the site of the rupture was thin, and the luminal surface was roughened with yellow streaks. The arterial wall adjacent to the rupture was thickened, white, firm, and less elastic than normal arterial walls. Cause of death was concluded to be acute exsanguination. Similar cases with sudden death have been reported in domestic cattle and humans. No risk factors, such as nutritional deficiencies, genetic predisposition, or blunt trauma, were identified in this case, and there was no gross or histologic evidence of generalized vascular disease.