The aorta is the largest blood vessel in your body. It carries blood from your heart to the rest of your body. The aorta extends from the chest to the abdomen, where it branches into the iliac arteries. The iliac arteries carry blood to the lower parts of the body and to the legs.
An abdominal aortic aneurysm (AAA) occurs when the portion of the aorta passing through the abdomen bulges because of a weakening of the vessel wall. The walls become thin and lose their ability to stretch.
The weakened sections of the wall may become unable to support the flow of blood through it and can burst. When an aneurysm bursts, it causes serious internal bleeding.
The condition is fairly common in older adults and is more common in men than in women. Risk factors for developing it are age, smoking, family history of AAA, atherosclerotic disease, and high blood pressure.