An abdominal aortic aneurysm (AAA) is a bulging or ballooning out in the wall of the abdominal aorta. The aorta is the artery through which blood flows out of the heart to the body. It is the “trunk” of the arterial tree and the largest artery in the body. All other arteries branch from the aorta.

Continuing from the upper (or thoracic) aorta, the abdominal aorta is the portion that travels the length of the abdomen. It carries blood down through the abdomen until it eventually splits off into two smaller iliac arteries that deliver blood to the pelvis and lower limbs.

Abdominal aortic aneurysms (AAA) are far more common than thoracic aortic aneurysms, comprising up to 75 percent of known aortic aneurysms. It is more common among men than women, among whites than blacks, and the likelihood of developing an abdominal aortic aneurysm increases with age. It is estimated that abdominal aortic aneurysms occur in up to 13 percent of all men and up to 6 percent of women over age 65.

Untreated, AAA can be a very dangerous medical condition as it can enlarge and rupture. An aortic aneurysm rupture can result in massive bleeding and often death (mortality rates for ruptured aneurysm are 70 to 90 percent). Therefore, early diagnosis and treatment of an aortic aneurysm is vital in preventing an aortic rupture.

The causes of AAA are unknown, but it is clear that smoking is a major risk factor, and it promotes the rate of aneurysm growth. AAA is more common in patients with atherosclerosis. Furthermore, high blood pressure (hypertension) is also associated with aneurysms, although to a lesser degree. Finally, recent research suggests that a genetic component may play a role in developing AAA.

Recent research suggests that inflammation may also play an important role in the development of aneurysms. Increasingly, inflammation is linked to a number of chronic health problems, including atherosclerosis. Studies have shown that patients with AAA tend to have elevated levels of inflammatory blood markers, such as C-reactive protein and interleukin-6. It's important to note, however, that there is a subclass of AAA called an inflammatory aneurysm. This is a distinct clinical entity from more conventional AAA and occurs in less than 10 percent of cases.

Aortic aneurysms are usually discovered during ultrasound exams or CT scans performed for other reasons. Symptoms can include abdominal, back or, more rarely, testicular pain. During the examination, the physician may note a bruit, a “whooshing” sound that a physician can hear with a stethoscope. There might be a pulsing mass in the abdomen of thin people where the aneurysm is pushing against the torso wall.

Once the aneurysm has ruptured, signs and symptoms often manifest themselves rapidly because of massive blood loss. These symptoms range from unconsciousness and sudden death to severe back pain and weakness (e.g., low blood pressure, dizziness, nausea, pale skin, “cold” sweat).

Approximately one half of patients with ruptures do not make it to the hospital before dying from the event. Of those who do receive surgery, approximately one half will survive operative repair, with the remainder dying in the hospital. It is for these reasons that the identification of AAA prior to rupture is so important.