Aortic Aneurysm Definition and Overview
Abnormal enlargement or bulging of the aorta, the largest blood vessel of the body, is not an unusual condition. Medical professionals refer to this as aneurysm of the great vessel, or aortic aneurysm. The enlargement usually affects only a small part of the vessel, so bulge is a more accurate description.
An aneurysm occurs when a segment of the vessel becomes weakened and expands. The pressure of the blood flowing through the vessel creates a bulge at the weak spot, much as an overinflated inner tube can cause a bulge in a tire. The bulge usually starts small and grows as the pressure continues. Aneurysms are dangerous because they can rupture, causing internal bleeding.
The aorta is an artery, meaning it carries oxygen-rich blood from the heart. It is the main artery coming from the heart.
Almost every artery in the body branches off of the aorta. These arteries supply blood to the brain, other vital organs (liver, stomach, small and large bowel, spinal cord) and nerves, bones, muscles, and cells that allow the body to function.
Bulging can occur in any artery in the body. It is most common in the arteries of the brain and in the abdominal aorta.
Arteries are muscular tubes. The wall of the artery is made up of three layers: the innermost layer (the intima), the middle layer (the media), and the outer layer (the adventitia). Bulges in an artery are classified as true aneurysm, false aneurysm, or dissection.
A related but different condition is aortic dissection. Dissection refers to a separation of the vessel wall, which allows blood to leak between the layers of the vessel. This further damages and weakens the vessel, placing it at much greater risk of bursting (rupture).
Because the abdominal aorta is such a large vessel, a ruptured abdominal aneurysm is a life-threatening event.
Each year, about 11,000 people in the United States die of a ruptured abdominal aneurysm, and aortic aneurysm is a contributing cause in about 17,000 deaths in the US in 2009.
Medically Reviewed by a Doctor on 9/17/2014
Shabir Bhimji, MD
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Abdominal aortic aneurysms (AAAs) represent a degenerative process of the abdominal aorta that is often attributed to atherosclerosis; however, the exact cause is not known. A familiar clustering of AAAs has been noted in 15-25% of patients undergoing repair of the problem.