Abdominal aortic aneurysm

An aneurysm is an abnormal widening or bulging of an artery. It occurs when a weakened area in the wall of an artery stretches and bulges as blood is pumped through it.

An abdominal aortic aneurysm (AAA) is an aneurysm that occurs in the section of the body's largest artery (the aorta) that runs through the abdomen. When an abdominal aortic aneurysm is identified, treatment may vary from watchful waiting to surgery. Abdominal aortic aneurysms, particularly those bigger than 5–6 centimetres in diameter, are at risk of rupture.

A ruptured abdominal aortic aneurysm is a medical emergency with a high risk of death, so surgery is required immediately. Approximately 230 deaths due to abdominal aortic aneurysm occur each year in New Zealand, most of which are in people aged 65 years or older.

Causes and risk factors

The reason abdominal aortic aneurysms develop is not fully understood. It is known that they tend to run in families, so it is thought that genetic factors may play a role. Other risk factors for developing abdominal aortic aneurysms include:

• Being a male aged over 65 years
• Atherosclerosis (a build-up of fatty deposits in the arteries)
• High blood pressure
• Smoking
• Inherited disorders (eg: Marfan syndrome, a disorder of the body’s connective tissues including blood vessels)
• Diseases that can weaken the aorta wall (eg: tuberculosis, syphilis).

Symptoms

Symptoms will depend on the location, nature, and size of the aneurysm. Sometimes no symptoms are present until the aneurysm is large and at risk of rupturing.

Symptoms of abdominal aortic aneurysms may be vague and non-specific such as backache or abdominal pain. Patients may also note a pulsating bulge in the abdomen — particularly when lying down. An abdominal aortic aneurysm is usually lined by a blood clot.

Occasionally, parts of this blood clot can be dislodged and travel in the bloodstream to block arteries to the leg (embolism), potentially causing a deep vein thrombosis (DVT). This may produce symptoms such as pain in the lower legs. Having an abdominal aortic aneurysm can also increase the risk of having a pulmonary embolism.

More acute symptoms, which may occur when an abdominal aortic aneurysm is expanding quickly or leaking, can include:

• A deep, pulsating, boring pain in the abdomen
• Pain in the left flank spreading down the left side towards the groin
• Lower back pain.

If an abdominal aortic aneurysm ruptures, sudden pain in the abdomen or lower back, dizziness and/or weakness may be felt. Loss of consciousness may also occur.

Diagnosis

Abdominal aortic aneurysms that do not produce any symptoms are often found during diagnostic tests or treatments for other medical conditions.

An ultrasound scan is usually the first diagnostic test done to confirm the presence of an abdominal aortic aneurysm. Other tests undertaken to confirm the diagnosis and pinpoint the location and size of the aneurysm may include CT and MRI scans, and x-rays. Tests to assess the functioning of the heart, lungs and kidneys may also be done.

Treatment

The two main treatment approaches include watchful waiting and surgical repair:

Watchful waiting

If the abdominal aortic aneurysm is small and is not causing any symptoms, the surgeon may recommend a “wait and watch” approach. This involves careful monitoring of symptoms and regular scans (usually every six months) to check for changes in the aneurysm. This usually involves ultrasound and CT scanning. High blood pressure will be treated with medications during this time to reduce the pressure on the aneurysm. Other conditions such as high blood cholesterol will also be treated. Lifestyle changes such as stopping smoking and achieving and maintaining a healthy body weight will also be recommended.

In some cases, a watchful waiting approach may be taken when the risks of surgery are deemed to outweigh the risks of monitoring the aneurysm, even though the aneurysm may be large and causing symptoms. This is often the case when other medical conditions are present — particularly those affecting the heart, lungs, or kidneys. Age is also a factor, as the risks of surgery increase with age.

Surgery

If the aneurysm is large or is causing symptoms, surgical repair of the aneurysm is usually recommended. The type of surgical repair used will depend on the location, size and shape of the aneurysm, the general state of health of the patient, and the urgency of the surgery.

In cases of aneurysm rupture, emergency surgery to repair the artery is required immediately.

The two main surgical techniques used to treat an abdominal aortic aneurysm are:

• Open Surgical Repair: during open surgical repair, an incision is made in the abdomen and the aneurysm is located and exposed. The aorta is clamped to prevent bleeding and the aneurysm is then opened and repaired, often using a synthetic patch or graft. A 1–2 stay in an intensive care unit is expected after surgery, followed by a 5–10 day stay in hospital. Complete recovery is usually achieved within two to three months.
• Endovascular Stent Graft: this technique involves inserting a specialised synthetic stent graft into the aneurysm via a tube inserted in an artery in the groin. Under x-ray guidance the graft is fed up into the aorta until it lies within the aneurysm. It is then expanded so that it snugly lines the inside of the aneurysm. This enables blood to flow through the aorta without putting pressure on the aneurysm. This technique only requires a small incision in the groin and has the advantage of a shorter hospital stay and a much quicker recovery time.

Prevention

Lifestyle changes can help to reduce the risk of developing an aortic aneurism and to prevent an existing aneurysm from getting bigger. This includes quitting smoking, maintaining a healthy body weight, and exercising regularly. Controlling existing conditions such as angina, high blood pressure, or high blood cholesterol is also important, as is regular monitoring of the aneurysm. Where there is a strong family history of aortic aneurysm, regular screening may be recommended.

References

Lee F.Y., Chen W.K., Chiu C.H., et al. Increased risk of deep vein thrombosis and pulmonary thromboembolism in patients with aortic aneurysms: A nationwide cohort study. PLoS One. 2017;12(6):e0178587.
Nair, N., et al. (2012). Population screening for abdominal aortic aneurysm: evaluating the evidence against screening criteria. N Z Med J. 2012;125(1350):72–83
Nair, N., et al. (2012). Abdominal aortic aneurysm disease in New Zealand: epidemiology and burden between 2002 and 2006. N Z Med J. 2012;125(1350):10–20
NHS (2020). Abdominal aortic aneurysm (Web page). Redditch: National Health Service (NHS) England. https://www.nhs.uk/conditions/repairofabdominalaneurysm/Pages/Introduction.aspx [Accessed: 19/11/20]
O’Toole, M.T. (Ed.) (2017). Aortic aneurysm. Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MI: Elsevier.
Rahimi, S.A. (2019). Abdominal aortic aneurysm (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/1979501-overview [Accessed: 19/11/20]

Last Reviewed: November 2020

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