A weakened portion of the abdominal aorta that expands. The abdominal aorta is the large artery in the abdomen that carries blood to the abdomen and legs. This weakened section can continue to expand, dissect, or rupture. A rupture of the aneurysm is a life threatening condition, leading to rapid blood loss and if left untreated death. A dissection of the aorta is a separation of the layers of the aorta and can occlude blood vessels to the abdominal organs (intestines, kidneys, etc.) and legs.