An aneurysm is an abnormal widening or ballooning of a portion of an artery, related to weakness in the wall of the blood vessel. Some common locations for aneurysms include:

• Aorta (the major artery from the heart) -- see abdominal aortic aneurysm and thoracic aortic aneurysm)
• Brain (cerebral aneurysm)
• Leg (popliteal artery aneurysm)
• Intestine (mesenteric artery aneurysm)
• Splenic artery aneurysm

It is not clear exactly what causes aneurysms. Defects in some of the parts of the artery wall may be responsible. In certain cases (abdominal aortic aneurysms), high blood pressure is thought to be a contributing factor. Some aneurysms are congenital (present at birth).

Atherosclerotic disease (cholesterol buildup in arteries) may contribute to the formation of certain types of aneurysms. Pregnancy is often associated with the formation and rupture of aneurysms of the splenic artery (an artery leading to the spleen).

The symptoms vary depending on the location of the aneurysm. Swelling with a throbbing mass at the site of an aneurysm is often seen if it occurs near the body surface. Aneurysms within the body or brain often have no symptoms

In the case of rupture, low blood pressure, high heart rate, and lightheadedness may occur. The risk of death after a rupture is high.

Physical exam, ultrasound examination, and CT scan are used to evaluate aneurysms.

Surgery is generally recommended. The timing and indications for surgery differ depending on the type of aneurysm.

Some people are candidates for endovascular stent repair. A stent is a tiny tube used to prop open a vessel. This procedure can be done with a major cut, so you recover faster than you would with open surgery. Not all patients with aneurysms are candidates for stenting, however.

With successful surgical repair, the outlook is often excellent.

The main complications of aneurysm include rupture, infection, and compression of local structures. Rupture of some types of aneurysms can cause massive bleeding, which is often fatal. This is commonly seen with abdominal aortic aneurysms, mesenteric artery aneurysms, and splenic artery aneurysms.

Rupture of aneurysms in the brain can cause stroke, disability, and death. Brain surgery for aneurysms can also result in these complications, if the aneurysm ruptures during surgery and bleeding cannot be controlled.

Infection of the aneurysm, which sometimes follows infection at other sites of the body, can lead to systemic illness and rupture. Clotting of the aneurysm occurs when blood stops moving inside the aneurysm, blocking further blood flow past the site of the aneurysm and depriving the tissues beyond of blood.

In certain cases, aneurysms can compress neighboring structures such as nerves, leading to neurologic problems, such as weakness and numbness. This can occur with popliteal artery aneurysms.

Call your physician for if you develop any new mass on your body, whether or not it is throbbing.

Control of high blood pressure may help prevent some aneurysms. Control of all risk factors associated with atherosclerotic disease (diet, exercise, cholesterol control) may help prevent aneurysms or their complications.