aortic aneurysm abnormal abdominal aorta morphology abdominal aorta aneurysm MPheno.ontology csmith a protruding sac formed by the dilation of the wall of the part of the descending aorta that begins at the diaphragm and continues to the point of the common iliac arteries, resulting from a weakening of the vessel wall MP:0010659 2010-10-19T10:48:39Z