What is an aneurysm?

An aneurysm is a bulging, weak area in the wall of a blood vessel. It may occur in any blood vessel, but most often develops in an artery rather than a vein. An aneurysm can be characterized by its location, shape, and cause. 

An aneurysm may be found in many areas of the body, such as the brain (cerebral aneurysm), the aorta (the largest artery in the body), the neck, the intestines, the kidney, the spleen, and the vessels in the legs (iliac, femoral, and popliteal aneurysms). The most common location of an aneurysm is the aorta, which carries oxygenated blood from the heart to the body. A thoracic aortic aneurysm is one that occurs in the chest cavity. An abdominal aortic aneurysm occurs in the abdomen. 

What causes an aneurysm to form?

An aneurysm may be caused by factors that result in the break down of the artery wall. The exact cause isn’t fully known. Atherosclerosis (hardening of the arteries) is thought to play an important role. Risk factors associated with atherosclerosis include:

Risk factors you can’t control:

  • Older age
  • Male
  • Family history
  • Genetic factors

Risk factors you can control:

  • High cholesterol
  • High blood pressure
  • Smoking
  • Diabetes
  • Obesity

Other specific causes of aneurysms are related to the location of the aneurysm. Examples of aneurysms in the body and their additional causes may include:

Type of aneurysm

Causes of aneurysms

Abdominal aortic aneurysm (AAA)

  • Atherosclerosis (especially in the part of the abdominal aorta below the kidneys, called an infrarenal aortic aneurysm)
  • Genetic disorders
  • Giant cell arteritis (a disease that causes inflammation of the temporal arteries and other arteries in the head and neck)
  • Infection

Cerebral aneurysm

  • Congenital (present at birth)
  • High blood pressure
  • Atherosclerosis
  • Head injury

Common Iliac artery aneurysm

  • Atherosclerosis
  • Pregnancy
  • Infection
  • Injury after lumbar or hip surgery

Femoral and popliteal artery aneurysm

  • Atherosclerosis
  • Injury
  • Congenital disorders

What are the symptoms of an aneurysm?

Aneurysms may have no symptoms. If symptoms are present, they will depend on the location of the aneurysm in the body. Pain is the most common symptom regardless of the aneurysm location.

Symptoms that may occur with different types of aneurysms may include:

Type of aneurysm


Abdominal aortic aneurysm (AAA)

Constant pain in abdomen, chest, lower back, or groin area

Cerebral aneurysm

Sudden severe headache, nausea, vomiting, visual disturbance, loss of consciousness

Common iliac aneurysm

Lower abdominal, back, or groin pain

Femoral and popliteal artery aneurysm

Pulsating of the artery in the groin (femoral) or on the back of the knee (popliteal), pain in the leg, sores on the feet or lower legs 

The symptoms of an aneurysm may look like other medical conditions or problems. Always see your doctor for more information.

How are aneurysms diagnosed?

What tests you’ll need depends on the location of the aneurysm. Along with a complete medical history and physical exam, tests for an aneurysm may include:

  • Computed tomography (CT or CAT) scan. This imaging test uses X-rays and computer technology to make horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than standard X-rays.
  • Magnetic resonance imaging (MRI). An MRI uses large magnets, radio frequency energy, and a computer to make detailed images of organs and structures in the body.
  • Echocardiogram (echo). This procedure evaluates the structure and function of the heart by using sound waves recorded on an electronic sensor that makes a moving picture of the heart and heart valves.
  • Arteriogram (angiogram). This is an X-ray image of the blood vessels used to evaluate various conditions, such as aneurysm, stenosis (narrowing of the blood vessel), or blockages. A dye (contrast) will be injected through a thin flexible tube placed in an artery. This dye will make the blood vessels visible on the X-ray.
  • Ultrasound. An ultrasound uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. An ultrasound is used to view internal organs as they function, and to assess blood flow through various vessels.