Aneurysm of the cranial mesenteric artery in a cow.

Exploratory laparotomy of an adult dairy cow, examined because of acute signs of persistent abdominal pain, revealed a firm pulsatile mass with associated fremitus just distal to the origin of the cranial mesenteric artery. The cow died acutely 2.5 days after surgery. A dilated, thin-walled, sacculated aneurysm, which had ruptured, was located along the proximal portion of the cranial mesenteric artery. It was postulated that the aneurysm developed secondary to structural defects in the arterial wall, but caused no clinical signs until enlargement and local tissue stretching or circulatory disturbances caused intestinal ischemia, resulting in abdominal pain. Aneurysms of visceral arteries in cattle should be considered as another differential diagnosis for signs of abdominal pain after more common causes such as severe bloat, mesenteric root volvulus, intussusception, cecal dilatation/volvulus, and uterine torsion have been excluded.