Abdominal Aortic Aneurysm
Risk Factors, Diagnosis, And Treatment Options


Abdominal aortic aneurysm, AAA, is a condition where there is a localized ballooning of a segment of the big blood vessel in the abdomen called the aorta. If this occurs with the width increasing to a certain size, it could burst, leading to severe internal bleeding. This can be very serious. See how to find out who could have this disease and the various treatment options here.

Albert Einstein is one of the well known persons to have died from this condition.

Abdominal aortic aneurysm diagram

It has been referred to as the silent killer, a ticking time bomb inside the abdomen, or more recently, a U-boat in the belly. Death is almost certain where this condition is undiagnosed and then ruptures.

AAA is the 13th cause of death in America, killing the same number of persons that die from more well known diseases like breast cancer or HIV.

Being a white male, aged over 60, a smoker and the presence of hypertension and a genetic predisposition are by far the most consistent predicator of vulnerability to this disease.

A simple ultrasound scan can pick up this condition and an effective treatment can be arranged to avert an untimely death.   

What Is Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) or aneurism is the abnormal widening and outward ballooning of a part or parts of the big blood vessel that carries blood from the heart down the body, called the aorta as it runs through the abdomen.

The aorta is the main blood vessel that carries blood directly from the heart through the chest and abdomen where it later divides into the right and left iliac arteries, that take blood to the legs. The aorta is the largest blood vessel in the body. It starts off from the left part of the heart, curves or arches downwards and backwards and continues down the chest (thorax).

In the chest, it is known as the Thoracic Aorta. A ballooning or aneurysm can occur here. If it does, it is called thoracic aortic aneurysm.

The aorta continues its downward course, passes through a natural opening in the diaphragm at the level of the tenth thoracic vertebra (spine bone) and becomes the abdominal aorta.

The most common site of ballooning of the aorta all across it's course is in the abdomen, just below the kidneys. The aorta gives off several major branches as it passes from the chest through the abdomen before it divides into iliac vessels. Two of such branches are the arteries to the right and left kidneys called the renal arteries.

Types Of AAA

Aneurysm of the abdominal aorta has been classified into a number of types. Such classifications are done on the basis of:

  • Size of the ballooning segment
  • Shape
  • Number of layers of the aorta affected or
  • Level at which the abnormal widening or ballooning of the artery occurs.

1. Diameter Or Size Of The Aneurysm

This is the most important way of classifying an abdominal aneurysm. Treatment options for aneurism of the abdominal aorta is based mainly on the size. There are three types of AAA described using size classification. They include:

  • Small Aneurysms - measures between 3cm to 4.5cm
  • Intermediate - 4.6 cm to 5.4 cm
  • Large aneurysm are those that measures 5.5cm or more.

2. Shape

There are two forms of aneurysm of the abdominal aorta based on shape. They are

  • Fusiform type (egg shaped) which is the most common type, usually caused by degeneration of the wall of the blood vessel.
  • Saccular type (bag shaped) which is tend to be caused by fungal infection of the wall of the aorta. This form is very rare. 

It is clearly helpful to know the shape, because treatment with antifungal medications may be needed if it is thought to be important in the aetiology of the disease.

3. Number Of Layers Of The Aorta Affected

Depending on the number of the walls of the aorta involved, aortic aneurysms can be described as true or false aneurysm.

  • True aneurysm has all three layers of the wall of the aorta involved in the ballooning. It is a true dilatation of the aorta. This is further divided into fusiform abdominal aortic aneurism (egg shaped) or saccular abdominal aortic aneurysm (bag shaped). The fusiform type of abdominal aortic aneurism is commoner, and may extend as long as over 20 cm to involve the iliac arteries.
  • False abdominal aortic aneurism is one where not all three layers of the wall of the aorta is involved in the ballooning. This usually occurs due to penetrating injury or infection.

4. Level At Which The Abnormal Widening Or Ballooning Of The Artery Occurs

  • Infra Renal Aortic Aneurysm. Nine out of ten cases (90%) of abdominal aortic aneurysm occurs below the point or level in the aorta where the renal (kidney) arteries have come off it. This is called infra renal abdominal aortic aneurysm. It is the safer variety since the kidneys may not be badly affected both before and after surgery.
  • Supra Renal Aortic Aneurysm. If the ballooning of the aorta were to occur before the aorta gives off the renal branches, it is called supra renal abdominal aortic aneurysm. This can have serious consequence for the kidneys, as the ballooning above the level of the kidneys may mean less blood flow pressure to the kidney. The repair also has increased risk. This type only happens in one out of ten cases (10%) of abdominal aortic aneurysm.

Aneurysm of the abdominal aorta could extend to involve one or both terminal branches (iliac arteries)

Cause of Abdominal Aortic Aneurysm

The exact cause of aortic aneurysm (AAA) is not known. However, the following factors are thought to contribute to the formation of an abdominal aneurysm:

  • Degeneration of the wall of the aorta due to chronic fat deposit (atherosclerosis). This is thought to be the main cause of abdominal aortic aneurism (90% of cases). This leads to loss of the natural elasticity of the wall of the aorta, thus can not expand and recoil as it would otherwise do. The wall starts to stretch and crack. Over a long time the wall thins out. It could start to leak from a very weak spot or even rupture without warning!
  • Another cause of aortic aneurysm is inherited defects in the structure of the proteins called collagen and elastin. These proteins are the building block of the wall of the aorta. Scanty or poor quality elastin causes the aorta to dilate (just as loosing the elastic on a nicker will lead to it sagging) and defective collagen encourages rupture. Thus a disease affecting both of these proteins means the strength of the blood vessels would be compromised. Examples of such inherited cause of abdominal aortic aneurysm are Ehlers Danlos Syndrome and Marfan disease or Marfan syndrome.
  • Injuries to the aorta either from direct force like seat belt injury following a car crash stab or from infections e.g. syphilis, fungi or mycotic infections which causes very high rate of rupture) can cause abdominal aortic aneurysm.
  • Inflammatory diseases of the arteries called arteritis
  • Subacute Bacterial endocarditis
  • Cystic medial necrosis (death of the wall of the aorta)

In the UK and US, abdominal aneurysm is believed to be present in 3 out of every 100 individuals after the age of 50. About 6 men are affected for every woman found with this disorder, and four times commoner in whites compared to blacks. It is also commoner after the age of 50, with a peak incidence around 70 years of age.

Other risk factors for abdominal aneurism include:

  • Presence of high blood pressure
  • Smoking
  • Family history of AAA.

It is believed that having diabetes protects you against developing this condition.

Symptoms

Abdominal aneurysm often do not cause any symptoms at the initial stage, unless they become large enough (up to 3 to 5cm). Aortic aneurysms are often accidentally picked up during routine examination or scans or X-ray for other medical reasons.

The common symptoms of abdominal aneurysm include:

  • Dull ache and fullness in the lower central abdomen and or lower back
  • Feeling of a pulsating lump in the lower central abdomen
  • Left side lower abdominal pain
  • left side lower back pain
  • Sudden onset lower abdominal pain that spread to the back with or without an associated fainting episode or collapse

These symptoms or combination of them could vary greatly from one person to the other. If you suspect that you might be having abdominal aortic aneurysm, please contact your doctor immediately. It is a serious surgical emergency, if it ruptures.

Treatment Options: To Operate Or Not To?

The exact size or point at which an operation is absolutely necessary for an aneurysm of the aorta is not known with certainty. However, it is generally agreed that a surgical repair of an aneurysm should take place if the abdominal aortic aneurism is more than 4.0cm.

Results from screen programs suggest that at 5.5cm, everyone with this condition should have it repaired. If at 3.5cm though, there is lower abdominal pain, or any symptoms with the aneurysm, then repair is warranted.

A planned repair of an aneurysm is best. The survival rate is about 98%. This is in sharp contrast to an emergency repair, following a burst, where successful operation rate drops from less then 50 percent to zero!

There are two main treatment options for repair of an abdominal aneurysm:

  1. Open Surgery
  2. Stent (key hole surgery) also called endovascular repair

It is generally agreed that the endovascular repair is safer, and more appropriate for a planned surgery especially if the aneurysm is below the kidney level, and it is not already ruptured.

Abdominal Aortic Aneurysm: Share Your Story

Do you or a close relative suffer with AAA? How was this diagnosed, and what size is it at the moment? Did you suffer with any symptoms? How was it treated - surgery, watchful waiting or EVAR (minimally invasive surgery)? Any complications?

Share your story here and help spread the vital message to let others know that this condition is not as uncommon as many would think.

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