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An aneurysm is an abnormal widening or ballooning of a portion of an artery due to weakness in the wall of the blood vessel.

See also:

• Abdominal aortic aneurysm
• Cerebral aneurysm
• Thoracic aortic aneurysm

It is not clear exactly what causes aneurysms. Some aneurysms are present at birth (congenital). Defects in some of the parts of the artery wall may be responsible.

Common locations for aneurysms include:

• The major artery from the heart (the aorta)
• The brain (cerebral aneurysm)
• In the leg behind the knee popliteal artery aneurysm)
• Intestine (mesenteric artery aneurysm)
• An artery in the spleen (Splenic artery aneurysm)

High blood pressure and high cholesterol may raise your risk of certain types of aneurysms. High blood pressure is thought to play a role in abdominal aortic aneurysms. Atherosclerotic disease (cholesterol buildup in arteries) may also lead to the formation of some aneurysms.

Pregnancy is often linked to the formation and rupture of splenic artery aneurysms.

The symptoms depend on the location of the aneurysm. If the aneurysm occurs near the body's surface, pain and swelling with a throbbing mass is often seen.

Aneurysms within the body or brain often cause no symptoms.

If an aneurysm ruptures, low blood pressure, high heart rate, and lightheadedness may occur. The risk of death after a rupture is high.

The health care provider will perform a physical exam.

Tests used to diagnose an aneurysm include:

• CT scan
• Ultrasound

With successful surgical repair, the outlook is often excellent.

The main complications of aneurysm include:

• Compression of nearby structures such as nerves, which may lead to weakness and numbness (most common with aneurysms that occur in the artery behind the knee)
• Infection, can lead to body-wide illness and rupture
• Rupture, which can cause massive bleeding that may lead to death

Massive bleeding is commonly seen with abdominal aortic aneurysms, mesenteric artery aneurysms, and splenic artery aneurysms.

Rupture of brain aneurysms can cause stroke, disability, and death. For more information, see: Cerebral aneurysm

Call your health care provider for if you develop a lump on your body, whether or not it is painful and throbbing.

Control of high blood pressure may help prevent some aneurysms. Following a healthy diet, getting regular exercise, and keeping your cholesterol at a healthy level may also help prevent aneurysms or their complications.

Isselbacher EM. Diseases of the aorta. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 78.

Zivin JA. Hemorrhagic cerebrovascular disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 432.

Hauser SC. Vascular diseases of the gastrointestinal tract. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 146.