Ruptured aortic aneurysm is a cause of sudden death that is more common in older male horses, especially breeding stallions. It usually occurs after breeding or following intense exercise. It is most commonly caused by a congenital aneurysm of the aortic root. The rupture results in massive bleeding into the chest or abdomen.

Collapse and death usually quickly follows rupture of an aortic aneurysm or ruptured aorta, usually within a few moments. But in some cases, it may not kill the horse immediately.

What follows can look similar to any other condition that results in signs of colic, along with signs of worsening heart failure. Other vessel ruptures can also cause massive bleeding into the abdomen or chest.

All of these occur without any external bleeding.

Diagnosis is usually done at post-mortem exam. In the standing horse, diagnosis requires ultrasound echocardiography. It may be possible to use echocardiography to visualize early development of aneurysm.

There is no practical treatment for this condition at this time.