Patient Information - Aortic Aneurysms


index of information on this page:
what is an aneurysm ??   how are aneurysms investigated ??
    why do aneurysms occur ??   do all aneurysms need surgery ??
why are aneurysms important ??   how are aneurysms repaired ??
                       what do they look like ??   risks and complications ??
how are aneurysms discovered ??   ruptured aortic aneurysms
        links


what is an aneurysm ?

An aneurysm is a stretching, dilatation and bulging of an artery that occurs as a result of weakening of the arterial wall and loss of its usual elastic properties.

Aneurysms can, in theory, occur in any artery in the body but are most common ( and of most clinical importance ) when they arise in the aorta - the main central artery of the body, which carries blood from the heart down through the chest and abdomen, giving off major branches to all the body's organs.

Aortic aneurysms, like many other types of arterial and heart diseases, are several times more common in men than women, possibly because of a protective effect of female hormones.

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Why do aneurysms occur?

Aneurysms which occur in the aorta are almost always associated with the common condition of atherosclerosis - degeneration, thickening and cholesterol deposition within the arteries associated with ageing. Risk factors for the early development of atherosclerosis include smoking, genetic risk factors (family history), high blood pressure, diabetes and high blood cholesterol levels.

Some rare aneurysms in other sites may be congenital or associated with other unusual inherited diseases.

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why are aortic aneurysms important ?

The vast majority of aortic aneurysms affect the lower section of the aorta in the abdomen, after it has given off its branches to the intestines and kidneys and before it splits into the two main arteries carrying blood into the legs  (iliac arteries).

In this position, an aneurysm can slowly develop and grow to considerable size without causing any symptoms at all. As it grows larger, an aneurysm carries an increasing risk of leaking and bursting without warning, causing catastrophic bleeding and a very high risk of death.

The fact that large aneurysms can remain undetected until they suddenly rupture is what makes the condition so potentially dangerous.

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what do aneurysms look like ?

Our web site contains a page of x-rays, photographs and diagrams which you may like to look at now, before returning here for further information:

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how are aneurysms discovered ?

Very occasionally, a patient may discover his or her own aneurysm by becoming aware of an abnormal pulsation in the centre of the abdomen. Many aneurysms, however, are difficult for either the patient or a doctor to feel on a routine abdominal examination and, because they rarely cause any warning symptoms, remain undetected for long periods of time.

Some aneurysms are visible on ordinary abdominal x-rays and nearly all are very easily detected by an ultrasound scan. A significant number are therefore discovered by accident when the patient has an x-ray or ultrasound scan for some completely separate reason. For example, the increased use of ultrasound scans by Urologists to investigate kidney, bladder and prostate problems has undoubtedly led to the discovery of many previously unsuspected aneurysms.

Because aneurysms often remain symptomless and undetected until they suddenly rupture, some Vascular Surgeons have become interested in large scale  ultrasound based screening programmes to detect unsuspected aneurysms.

      read about Gloucestershire's aneurysm screening programme

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how are aneurysms investigated ?

The mainstay of aneurysm investigation is the abdominal ultrasound scan. This is a quick, simple and completely painless investigation which gives an accurate measurement of the aorta's maximum diameter. An ultrasound scan may be used to make the initial diagnosis or to follow any changes in size of a small aneurysm with repeat scans every few months.

When more detailed information is required, such as the precise upper and lower extent of the aneurysm before an operation, a CT or MRI scan may be performed.

Prior to undergoing operation to repair an aneurysm, patients may require a variety of further investigations, particularly of their cardiac function, in order to establish their fitness to undergo major surgery.

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do all aneurysms need surgery ?

Many smaller aneurysms never require an operation to repair them but are kept under careful surveillance with repeat ultrasound scans to ensure that they are not increasing in size.

Larger aneurysms begin to carry an increased risk of sudden rupture and therefore the risks of a major operation to repair them may become justified. It is the responsibility of the Vascular Surgeon to assess, as far as possible, the chances of aneurysm rupture versus the risks of corrective surgery in each individual patient and to advise accordingly.

As an approximate guide, the maximum normal diameter of the adult male aorta is considered to be 2.5 cms. Moderate dilatation up to 4 cms is seen in about 4% of males over the age of 65 years and carries an extremely small risk of rupture. Most Vascular Surgeons would advise 6 or 12 monthly repeat ultrasound scans for these very small aneurysms and would only consider surgery for those that continue to grow larger.

Above 6 cms diameter, the risk of rupture rises dramatically and probably approaches 10% risk of rupture per year. Most Vascular Surgeons would consider elective surgical repair of aneurysms of this size or larger, taking into account also the patient's age, other medical conditions, fitness for anaesthesia and life expectancy.

Between 4 cms and 6 cms is a slightly "grey" area where the benefits of surgical repair are far less obvious. A number of clinical trials, including the UK Small Aneurysm Trial, are currently in progress in order to further assess the risks and benefits of surgery on aneurysms within this size range.

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how are aneurysms repaired ?

The current standard operation for abdominal aortic aneurysms was developed in the mid 1950s and consists of replacement of the weakened, dilated portion of the aorta with an artificial graft manufactured from a polyester material (Dacron).

The abdomen is opened to expose the aorta which is then temporarily clamped above and below the aneurysm. It is usually possible to place the upper clamp just below the origins of the branches to the kidneys so that the kidneys continue to receive blood flow throughout the operation. Blood flow to the legs is interrupted while the aorta is clamped but this is not usually a problem, particularly if heparin is administered to prevent any static blood from clotting.

The aneurysm itself is then incised, opened throughout its length and any contained blood clot and debris is removed. The graft is inserted by sewing it to the normal calibre aorta above and below the opened aneurysm so that it lies within what was the inside of the aneurysm. Many aneurysms can be repaired with a simple, straight tubular graft although if the aneurysm extends further downwards, a "trouser" shaped graft can be used to replace the main arteries to the pelvis and legs (iliac arteries) as well.

When the clamps have been removed and blood flow is re-established through the graft, the wall of the aneurysm is closed over the graft, largely to protect it from becoming adherent to loops of intestine.

Most patients will be monitored in an Intensive Care Unit or High Dependency Unit for the first 24 to 48 hours after operation and will be fit for discharge home after 7 to 10 days. Full convalescence from any major operation of this type may be expected to take up to 4 weeks.

In the last few years there has been considerable research into less invasive methods of repairing aortic aneurysms, avoiding the need for a major open abdominal operation. These so called "endovascular" procedures usually involve passing a graft into the inside of the aneurysm through the femoral artery in the groin. The graft is placed in position using very careful and accurate x-ray control and fixed in place to the normal calibre aorta, above and below the aneurysm, by expandable metal "stents". The technical difficulties which have to be overcome in developing these methods are enormous, particularly those of achieving a safe and lasting blood-tight seal at the ends of the graft in arteries which may vary considerably in size and which may be extremely elongated and distorted.

It seems unlikely that endovascular techniques will ever be suitable for the repair of all shapes and sizes of aneurysms but they do offer the prospect of a much less major operation and shorter hospital stay. At present, a number of different systems are undergoing evaluation at various centres throughout the world and the majority of Vascular Surgeons are awaiting the results of these trials before endovascular repair is widely adopted as a standard technique.

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what are the risks and complications of aneurysm surgery ?

Any major abdominal operation under a general anaesthetic carries the risk of major complications and death.

Respiratory complications can occur after any painful abdominal operation which discourages deep breathing and coughing, particularly when the patients are likely to be elderly and to have smoked in the past. These risks can be minimised by intensive post-operative chest physiotherapy and the use of epidural anaesthesia to reduce post-operative pain.

Bleeding is clearly a risk in an operation which involves major blood vessels and great care is taken during aneurysm surgery to ensure, as far as possible, that suture lines at the ends of the graft are fully sealed and blood-tight. Blood loss during a routine operation typically averages 500 to 1000 mls and may be much greater in technically difficult and prolonged operations. Most patients will require blood transfusion during or after the operation. The use of "bank" blood (with its associated small risks of transmission of infections and adverse reactions) can be reduced or even eliminated completely by the "pre-donation" of patient's own blood in the 2 to 3 weeks before operation, by the temporary removal of 500 to 1000 mls of the patient's own blood at the beginning of surgery to be returned as the procedure finishes and by the use of blood salvage machines which retrieve blood lost during the operation and prepare it for retransfusion.

The single greatest source of post-operative complications in aneurysm surgery is the heart. Most patients undergoing aneurysm repair will be at least 65 years old, many will have some degree of coronary artery disease and many will have a history of previous heart attack, angina or hypertension. Careful preoperative investigation is needed to identify and, where possible, treat these pre-existing problems. Skilled anaesthesia is required during the procedure to minimise strain on the heart caused by blood loss and the major changes in blood flow which occur with clamping and unclamping the aorta. Careful post-operative monitoring in ITU can help to ensure optimum heart and lung function in the important first 24 hours.

Overall, elective aneurysm repair carries a risk of death of approximately 4% - 5% in hospitals which perform a reasonable number of these operations. This risk should, however, be compared to the risk of death from sudden rupture of an aortic aneurysm which exceeds 80%.

95% of patients will make a good recovery from elective aneurysm surgery and will have returned fully to their pre-operative level of health and activity within a month or two. Long term complications after successful aneurysm repair are comparatively rare and it is unusual for there to be later problems with the graft or with further aneurysm formation.

Interference with sexual function in men can occur after aneurysm surgery and it is often wise to discuss this possibility with patients in whom this may be important. Impotence or failure of erection can occur if the blood vessels in the pelvis which supply the penis are involved in the aneurysm process. A more common complication is failure of ejaculation, which is produced by the almost unavoidable damage to nerve fibres which surround the lower end of the aorta.

Patients who have undergone  successful aneurysm repair have an average life expectancy afterwards which is almost identical to that of the normal population of the same age.

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ruptured aortic aneurysms

Rupture or leaking of an abdominal aortic aneurysm occurs when the diseased, stretched wall of the aorta finally begins to tear under the pressure of blood within it and allows blood to escape, either into the tissues surrounding the aorta in the back of the abdomen or freely into the abdominal cavity.

The rupture may cause sudden, rapidly fatal blood loss or may begin more slowly with a series of smaller "warning" bleeds associated with abdominal and back pain, progessing over a matter of hours or days to massive bleeding. Without treatment, a leaking aortic aneurysm leads inevitably to death.

Rupture of aortic aneurysms is responsible for an estimated 10,000 deaths annually in the UK, the majority in males over the age of 70 years. Accurate figures are difficult to obtain since sudden collapse and death in an elderly patient, who may be known to suffer from heart disease, may well be attributed to a heart attack if an aneurysm has not previously been diagnosed and post mortem examination is not performed. Official statistics, based on doctors' entries on death certificates, are therefore likely to be an underestimate of the true incidence of aneurysm rupture.

It is estimated that less than half of all patients suffering a ruptured aortic aneurysm will reach hospital alive and, of those that do, less than half will survive emergency surgery to repair the aneurysm. The overall risk of death if an aneurysm ruptures is therefore in the region of 80%. Complications of massive bleeding, heart attacks, kidney failure and respiratory problems are many times more common in emergency procedures than in planned operations.

The operative technique used to repair a leaking aortic aneurysm is similar to that used in planned cases but the operation is obviously carried out in far less favourable circumstances, resulting in a much higher operative death rate.

In many cases, rupture is often the presenting symptom of a previously undiagnosed and unsuspected aneurysm. This has led to an interest in the possibility of ultrasound screening of the elderly male population,  in order to allow more aneurysms to be repaired before they rupture. Screening of males as they reach the age of 65 has been carried out in Gloucestershire since 1990 and it is hoped that this project will be able to demonstrate a clear reduction in deaths from aneurysm rupture within the next few years.

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This page compiled by Brian P Heather  MS FRCS
on behalf of the Gloucestershire Vascular Group