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Abdominal Aortic Aneurysm

Abdominal Aortic Aneurysm

What is an abdominal aortic aneurysm?

Illustration of the anatomy of the aorta
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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.

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.

Illustration of infrarenal abdominal aortic aneurysm
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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 not an enlargement of any of the layers 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 dissection.

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.

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. 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.

Abdominal aortic aneurysms may also cause a pulsing sensation, similar to a heartbeat, in the abdomen.

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:

A small aneurysm or one that does not cause symptoms may not require surgical treatment until it reaches a certain size or is rapidly increasing in size over a short period of time. Your doctor may recommend "watchful waiting." This may include an ultrasound, duplex scan, or CT scan every 6 months to closely monitor the aneurysm, and blood pressure medication may be used to control high blood pressure.

If the aneurysm is causing symptoms or is large, surgery may be recommended by your doctor.

What is aortic dissection?

An aortic dissection, although uncommon, begins with a tear in the inner layer of the aortic wall. The aortic wall is made up of three layers of tissue. When a tear occurs in the innermost layer of the aortic wall, blood is then channeled into the wall of the aorta, separating the layers of tissues. This generates a weakening in the aortic wall with a potential for rupture. Aortic dissection can be a life-threatening emergency.

Illustration of aortic dissection
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What causes aortic dissection?

The cause of aortic dissection is still under investigation. However, several risk factors associated with aortic dissection include, but are not limited to, the following:

What are the symptoms of aortic dissection?

The most commonly reported symptom of an acute aortic dissection is severe, constant pain, sometimes described as "ripping" or "tearing," and located in the chest, the middle of the abdomen, the lower back, or the pelvis area. The pain may be "migratory," moving from one place to another, according to the direction and extent of the dissection.

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

How is aortic dissection diagnosed?

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

The physician will determine the most appropriate examination. When a diagnosis of aortic dissection is confirmed, immediate intervention is necessary. Medical intervention or surgery will be required depending on the location of the aortic dissection.

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