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Abdominal aortic aneurysm

This factsheet is for people who have had an abdominal aortic aneurysm (AAA) or for people who would like information on abdominal aortic aneurysms.

An abdominal aortic aneurysm is a dilation (widening or bulge) of a portion of the aorta, usually at a weak spot in the aortic wall. About 1 in 20 people in the UK over the age of 65 develop an abdominal aortic aneurysm. If an abdominal aortic aneurysm ruptures (bursts) it can be fatal. Surgery can repair the aorta - this can be emergency surgery if the aneurysm ruptures or elective (planned) surgery if a patient has an aneurysm that is large and the risk of rupture is high.

About aortic aneurysms

What is the aorta?

The aorta is the largest artery in the body. It carries all the blood that is pumped out of the heart and distributes it, via its many branches, to all the organs of the body. The aorta projects upwards from the heart in the chest and then arches downwards, travelling through the chest (the thoracic aorta) and into the abdomen (the abdominal aorta).

The normal diameter of the abdominal aorta is about 2 to 3cm (about 1 inch).

What is an aortic aneurysm?

An aortic aneurysm is a thin weakened section of the wall of the aorta that bulges outward. Most aortic aneurysms occur in the section of the aorta that passes through the abdomen and are called abdominal aortic aneurysms. A few occur in the part of the aorta in the chest that is near the heart, and are called thoracic aortic aneurysms.

As the wall of the aneurysm is weaker than a normal artery wall it may not withstand the pressure of blood inside. This may cause it to rupture (burst).

The chance of an abdominal aortic aneurysm rupturing depends on the size of it.

• If the aneurysm is less than 5cm wide the chances of rupture are small (National Institute of Clinical Excellence - NICE - statistics show that for every 100 people with a small aneurysm, the aneurysm may rupture in up to 5 of those people after 8 to 9 years).
• If the aneurysm is greater than 5cm wide the chances of rupture are higher (NICE statistics show that for every 100 people with a large aneurysm, the aneurysm may rupture in about 25 of those people after 8 to 9 years) - and the risk increases with increasing size.

Illustration of the aorta and an aneurysm

Symptoms

Many people have an abdominal aortic aneurysm for years before any symptoms develop, if they develop at all. If you do get symptoms, they may vary according to where the aneurysm is in your body. If an aneurysm is in your abdomen, symptoms may include:

• a pulsating feeling in your abdomen
• abdominal pain
• back pain

Complications

If an abdominal aortic aneurysm becomes very large and ruptures (bursts) it can cause excruciating pain in the abdomen and back. A ruptured abdominal aortic aneurysm causes severe internal bleeding which is often fatal unless emergency surgery is carried out to repair the rupture.

Causes

The main cause of aortic aneurysms is atherosclerosis. This is a condition in which fatty deposits are laid down in the walls of arteries. The deposit is called an atheroma. This weakens the wall and makes the walls less elastic and weaker as a result.

There are certain factors that may make you more likely to develop atherosclerosis and therefore an aortic aneurysm including:

• your sex (men are more likely to develop an aortic aneurysm than women)
• smoking
• your age - aortic aneurysms are more common in older people - particularly in the 60-69 age group
• your family history - men who have a first degree relative that have had an aortic aneurysm have a higher chance of having an aortic aneurysm
• high blood pressure
• if you do little physical activity
• if you are overweight

Other less common causes of aortic aneurysm include:

• trauma to the aorta, for example a crush injury to the chest following a car accident
• certain infections including syphilis
• rare hereditary conditions such as Marfan's syndrome (a major cause of thoracic aortic aneurysm, the type affecting the part of the aorta near the heart in the chest)

Diagnosis

Abdominal aortic aneurysms can be diagnosed from their symptoms when they occur. They may also be found on routine physical examination and chest and abdominal X-rays.

When your doctor examines you, he or she may feel a pulsating mass in your abdomen which may be tender if an abdominal aortic aneurysm is large. If your doctor suspects an aneurysm, he or she will request tests including those below.

• An abdominal ultrasound scan is the most common test to detect an aneurysm. It can also measure the size of the aneurysm. For more information on ultrasound scans please see the separate BUPA factsheet, Ultrasound.
• Other scans such as computerised tomography (CT) may also be performed. This is very useful for determining the exact position of the aneurysm. For more information on CT scans, please see the separate BUPA factsheet, CT scan.

Screening

At present there is not a national screening programme to detect abdominal aortic aneurysms. However, the Government is considering plans to introduce a programme. Scans are available from private clinics and hospitals such as BUPA.

Treatment

Your treatment for an aortic aneurysm will depend on your symptoms and the size of the aneurysm.

Emergency surgery is needed if an abdominal aortic aneurysm ruptures. This is a major operation and carries significant risks. A small number of people will die during, or shortly after, an emergency operation.

The decision to have elective surgery is based on the size of the aneurysm.

• If you have a small abdominal aortic aneurysm (less than 5cm wide), the risk of death caused by surgery is higher than the risk of rupture. Therefore surgery is usually not advised but you will need regular ultrasound checks to see if the aneurysm grows over time. It will also be important to manage your condition by managing risk factors such as smoking and your diet.
• If you have an aneurysm larger than 5cm wide, surgery is usually advised. For larger aneurysms the risk of rupture is usually higher than the risks of surgery. However, this will depend on your personal state of health. For some people the risks of surgery will still outweigh the benefits. Your doctor will discuss your options and advise you if surgery is the best treatment for you.

There are two main surgical options for an abdominal aortic aneurysm.

Open surgery

Aortic aneurysm (open surgery) animation

In the traditional surgical method, your surgeon will make an opening in your abdomen. The blood vessel will then be opened at the site of the aneurysm and be replaced with a graft. The graft can be made with a piece of blood vessel taken from another place in the body or it can be synthetic. A synthetic graft is made out of an elastic material and is similar to a normal healthy aorta. It gives your artery support to prevent the aneurysm getting bigger.

Minimally invasive surgery and stent insertion

Aortic aneurysm (minimally invasive surgery) animation

Alternatively your surgeon may place a stent graft into your aorta. A stent graft is a graft placed over an artificial piece of rigid tubing called a stent. This is a more recently developed minimally invasive technique and is not suitable for everybody. A small cut will be made in your groin and the stent graft will be passed up inside one of your leg arteries until it reaches the area of the aneurysm. The stent will be positioned so that your blood vessel is repaired and the aneurysm is protected from further pressure. This method does not involve open surgery.

Your surgeon will advise you which procedure is best for you.

Prevention

There are several things you can do to reduce your chance of developing an aneurysm:

• do not smoke
• have your blood pressure checked regularly
• exercise regularly
• maintain a healthy weight

You should also have regular medical check ups if you have a family history of arterial disease so that any problems can be detected early.

Further information

• The British Heart Foundation
  0845 0 70 80 70
  www.bhf.org.uk
• The Vascular Society of Great Britain and Ireland
  020 7973 0306
  www.vascularsociety.org.uk

Sources

• Aortic aneurysm. UK Department of Health. PRODIGY patient information leaflet.
  www.prodigy.nhs.uk
  accessed 4 January 2006
• Stent-graft placement in abdominal aortic aneurysm. National Institute for Clinical Excellence (NICE). September 2003.
  www.nice.org.uk
• Aortic aneurysm. FAQs. British Heart Foundation. October 2004.
  www.bhf.org.uk
• Stent-graft placement in abdominal aortic aneurysm. Understanding NICE guidance - information for people considering the procedure, and for the public. National Institute for Clinical Excellence (NICE). Procedure Guidance 163. March 2006.
  www.nice.org.uk
• Abdominal aortic aneurysms. British Heart Foundation. Factfile 03/2003.
  www.bhf.org.uk
• McLatchie GR, Leaper DJ. Oxford Handbook of Clinical Surgery. Oxford: Oxford University Press, 2002.840+
• Longmore M, Wilkinson I, Torok E. Oxford Handbook of Clinical Medicine. Oxford: Oxford University Press, 2001:468.

Reviewed by Dr James Quekett, Bsc.MB Ch.B MRCGP DRCOG DFFP, partner/principal general practitioner at Rowcroft Medical Centre.

Published by BUPA's health information team, healthinfo@bupa.com, July 2006.

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