The aorta is the body’s main artery, starting at the heart’s left ventricle and extending down to the abdomen. If a portion of the aorta is weak, that area can swell and become thin and fragile. This swelling, known as an aneurysm, indicates the risk of rupture and heavy internal bleeding. While the exact cause of an abdominal aortic aneurysm is unknown, tobacco use, trauma, genetics, high blood pressure, atherosclerosis, infection, or blood vessel diseases can cause this condition. The course of treatment depends on the size and growth rate of an aortic aneurysm.