Characterization of rupture of abdominal artery aneurysm in dairy cattle.

In this retrospective study, the authors describe the gross and histologic changes associated with rupture of an abdominal artery aneurysm in 33 mature female Holstein cattle between January 1980 and June 2005 from 29 farms in upstate New York and northern Pennsylvania. Over this period, there was an increase in the number of cases submitted for necropsy per year, and a seasonal trend did not exist. Affected animals ranged from 2.5 to 5.5 years of age. Grossly affected cattle exhibited marked hemoabdomen. There was marked dilation and rupture of the abdominal aorta or one of its branches, including the mesenteric, left gastric, celiac artery, right ruminal artery, or left ruminal artery. Histologically, the tunica media of the affected arteries was often thin and irregular in width with disrupted, fragmented, and coiled elastin. Granulation tissue and hemorrhage was localized at the site of rupture. There was mild-to-marked hyperplasia of the tunica intima that was irregular and disorderly with adjacent smooth-muscle hyperplasia within the tunica media. In addition, in a fraction of cases, there was mild-to-moderate mucinous change (48%) and mineralization (30%) within the tunica media. To the authors' knowledge, this is the first description of the gross and histologic changes in Holstein cows with abdominal artery aneurysm and rupture.