Abdominal Aortic Aneurysm

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What is an abdominal aortic aneurysm?

An abdominal aortic aneurysm, also called AAA or triple A, is a bulging, weakened area in the wall of the aorta (the largest artery in the body) resulting in an abnormal widening or ballooning greater than 50 percent of the normal diameter (width).

The aorta extends upward from the top of the left ventricle of the heart in the chest area (ascending thoracic aorta), then curves like a candy cane (aortic arch) downward through the chest area (descending thoracic aorta) into the abdomen (abdominal aorta). The aorta delivers oxygenated blood pumped from the heart to the rest of the body.

Illustration of the anatomy of the aorta

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The most common location of arterial aneurysm formation is the abdominal aorta, specifically, the segment of the abdominal aorta below the kidneys. An abdominal aneurysm located below the kidneys is called an infrarenal aneurysm. An aneurysm can be characterized by its location, shape, and cause.

The shape of an aneurysm is described as being fusiform or saccular which helps to identify a true aneurysm. The more common fusiform shaped aneurysm bulges or balloons out on all sides of the aorta. A saccular shaped aneurysm bulges or balloons out only on one side.

A pseudoaneurysm, or false aneurysm, is an enlargement of only the outer layer of the blood vessel wall. A false aneurysm may be the result of a prior surgery or trauma. Sometimes, a tear can occur on the inside layer of the vessel resulting in blood filling in between the layers of the blood vessel wall creating a pseudoaneurysm.

Illustration of infrarenal abdominal aortic aneurysm

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The aorta is under constant pressure as blood is ejected from the heart. With each heart beat, the walls of the aorta distend (expand) and then recoil (spring back), exerting continual pressure or stress on the already weakened aneurysm wall. Therefore, there is a potential for rupture (bursting) or dissection (separation of the layers of the aortic wall) of the aorta, which may cause life-threatening hemorrhage (uncontrolled bleeding) and, potentially, death. The larger the aneurysm becomes, the greater the risk of rupture.

Because an aneurysm may continue to increase in size, along with progressive weakening of the artery wall, surgical intervention may be needed. Preventing rupture of an aneurysm is one of the goals of therapy.

Illustration of types of aneurysms

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What causes an abdominal aortic aneurysm to form?

An abdominal aortic aneurysm may be caused by multiple factors that result in the breaking down of the well-organized structural components (proteins) of the aortic wall that provide support and stabilize the wall. The exact cause is not fully known.

Atherosclerosis (a build-up of plaque, which is a deposit of fatty substances, cholesterol, cellular waste products, calcium, and fibrin in the inner lining of an artery) is thought to play an important role in aneurysmal disease, including the risk factors associated with atherosclerosis, such as:

Other diseases that may cause an abdominal aneurysm include:

What are the symptoms of abdominal aortic aneurysms?

Abdominal aortic aneurysms may be asymptomatic (without symptoms) or symptomatic (with symptoms).

About three of every four abdominal aortic aneurysms are asymptomatic and may be found upon routine physical examination by the discovery of a pulsating mass in the abdomen. An aneurysm may also be discovered by x-ray, computed tomography scan (CT scan), or magnetic resonance imaging (MRI) that is being done for other conditions. Since abdominal aneurysm may be present without symptoms, it is referred to as the "silent killer" because it may rupture before being diagnosed.

Pain is the most common symptom of an abdominal aortic aneurysm. The pain associated with an abdominal aortic aneurysm may be located in the abdomen, chest, lower back, or groin area. The pain may be severe or dull. The occurrence of pain is often associated with the imminent (about to happen) rupture of the aneurysm.

Acute, sudden onset of severe pain in the back and/or abdomen may represent rupture and is a life threatening medical emergency.

The symptoms of an abdominal aortic aneurysm may resemble other medical conditions or problems. Always consult your physician for more information.

How are aneurysms diagnosed?

In addition to a complete medical history and physical examination, diagnostic procedures for an aneurysm may include any, or a combination, of the following:

Treatment for abdominal aortic aneurysms:

Specific treatment will be determined by your physician based on:

Treatment may include:

Asymptomatic aneurysms may not require surgical intervention until they reach a certain size or are noted to be increasing in size over a certain period of time. Parameters considered when making surgical decisions include, but are not limited to, the following:

For symptomatic aneurysms, immediate intervention is indicated.

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