Abdominal Aortic Aneurysm (AAA)

What an abdominal aortic aneurysm is

The aorta carries blood from the heart down through the chest and abdomen, where it divides into the arteries to the legs. A normal abdominal aorta is about 2 cm (0.8 inches) wide. In an aneurysm, the wall weakens, loses its elastic and collagen fibers, and gradually balloons outward. Most AAAs form below the kidney arteries (infrarenal).

The larger the aneurysm, the faster it tends to grow and the higher the chance of rupture. Typical growth is about 1 to 4 mm a year for small aneurysms and faster for larger ones.

These figures are approximate ranges from vascular surgery guidelines. Women's aneurysms rupture at smaller sizes than men's.

Symptoms

Most AAAs cause no symptoms and are found by chance on an ultrasound, CT scan or X-ray done for something else. When symptoms occur, they may include:

• a pulsing feeling near the belly button
• a deep, constant ache in the belly, lower back or side
• pain spreading to the groin, buttocks or legs

Signs of a ruptured aneurysm

Rupture causes:

• sudden, severe pain in the belly or back
• dizziness, sweating, a fast heartbeat and fainting from blood loss
• nausea and vomiting

About 8 in 10 people with a ruptured AAA die, many before reaching the hospital. Rapid emergency surgery is the only treatment, which is why screening and planned repair matter.

Causes and risk factors

• Smoking: the biggest risk factor. Smokers are several times more likely to develop an AAA, and smoking speeds growth.
• Age: most occur after 65.
• Male sex: men are affected about 4 to 6 times more often than women, though aneurysms in women are more likely to rupture.
• Family history: a first-degree relative with an AAA raises your risk.
• Atherosclerosis, high cholesterol and peripheral artery disease.
• High blood pressure.
• Connective tissue disorders: Marfan syndrome, Ehlers-Danlos syndrome and Loeys-Dietz syndrome, which more often cause thoracic aortic aneurysms.
• Rarely: infection of the aortic wall, inflammation (vasculitis) and trauma.

Diabetes is, unusually, linked to a lower risk of AAA.

Screening

The US Preventive Services Task Force recommends a one-time ultrasound screening for men aged 65 to 75 who have ever smoked (at least 100 cigarettes in their life). Men in this age group who have never smoked may be screened selectively, for example with a family history. In the UK, all men are invited for screening at 65. Screening is quick, painless and reduces deaths from AAA.

Diagnosis

• Abdominal ultrasound: the standard screening and monitoring test.
• CT angiography: gives precise measurements and anatomy, needed to plan repair.
• Physical exam: a doctor may feel a pulsing mass, though many aneurysms cannot be felt, especially in larger people.

Treatment

Small aneurysms: surveillance

Aneurysms below the repair threshold are monitored with ultrasound. Typical intervals from US vascular surgery guidance:

During surveillance:

• stop smoking, which slows growth
• control blood pressure and cholesterol, usually with a statin
• take aspirin if advised for heart and artery protection
• stay active; moderate exercise is safe
• report any new belly or back pain promptly

When repair is recommended

Repair is usually advised when:

• the aneurysm reaches 5.5 cm in men or 5.0 to 5.4 cm in women
• it grows more than 1 cm a year, or about 0.5 cm in 6 months
• it causes symptoms such as pain or tenderness
• it ruptures (emergency repair)

Repair options

Complications

• rupture and life-threatening bleeding
• clots from the aneurysm blocking smaller arteries in the legs or toes
• after EVAR: endoleaks (blood still flowing into the sac), graft movement or blockage
• after open repair: heart and lung complications, kidney problems and hernia at the incision

Outlook

Small aneurysms under surveillance rarely rupture. Planned repair has good results, with low early death rates in specialist centers. After repair, most people return to normal activities. Having an AAA is also a sign of widespread artery disease, so managing heart risk factors is important for long-term health.

Frequently asked questions

What are the symptoms of an abdominal aortic aneurysm?

Most abdominal aortic aneurysms cause no symptoms. Some people notice a pulsing feeling in the belly, or a deep ache in the belly or back. A ruptured aneurysm causes sudden severe belly or back pain, dizziness and collapse, and needs emergency care.

What size of abdominal aortic aneurysm needs surgery?

Repair is usually recommended at 5.5 cm in men and 5.0 to 5.4 cm in women, or sooner if the aneurysm is growing quickly (more than 1 cm a year) or causing symptoms. Smaller aneurysms are monitored with regular ultrasounds.

Who should be screened for AAA?

In the US, men aged 65 to 75 who have ever smoked should have a one-time abdominal ultrasound. Men in that age group who never smoked may be screened if they have other risks, such as a family history. Talk with your doctor about your own risk.

Can an abdominal aortic aneurysm shrink?

No. An aneurysm does not shrink on its own. Stopping smoking and controlling blood pressure can slow its growth. After EVAR, the aneurysm sac often shrinks because blood no longer flows into it.

What should you avoid with an abdominal aortic aneurysm?

Avoid smoking, which speeds growth. Keep blood pressure controlled. Very heavy straining or lifting is often discouraged for large aneurysms, though moderate exercise is safe and encouraged. Ask your vascular team about specific limits for your aneurysm size.