Abdominal Aortic Aneurysm
The aorta is the major blood vessel that supplies blood to the body. An abdominal aortic aneurysm (AAA) is an enlarged and weakened area in the lower part of the wall of the aorta. A normal aorta is approximately one inch or less in diameter and it runs from the heart passing through the center of the chest and abdomen. In general, aneurysms can develop anywhere along the length of aorta. Aneurysms in the upper part of the aorta are called thoracic aortic aneurysms. But, aneurysms are more common in lower parts of aorta and called as abdominal aortic aneurysms. These aneurysms may also be referred to as AAA or triple A.
An aneurysm can grow to be more than five inches in diameter. Due to high pressure of blood flowing through the artery, the weakened area enlarges like a balloon. It is more common to see large aneurysms bursting as compared to the smaller ones.
This results in internal bleeding that can lead to death unless treated immediately by an experienced cardiovascular surgeon. AAAs are considered a serious health condition because they can burst or rupture. Only about half of patients with a ruptured AAA who get to a hospital survive. Treatment of AAA may vary from watchful waiting to emergency surgery depending on the size and rate at it is growing. Once a diagnosis of AAA is made, doctors will closely monitor it so that surgery can be planned if it's necessary. It is very risky to wait for surgery till the time AAA ruptures.
Risk factors for abdominal aortic aneurysm include:
- Increasing Age. AAAs are seen most often in people age 65 and older.
- Smoking. Smoking is a strong risk factor for the development of an abdominal aortic aneurysm. The duration of smoking is directly proportional to the risk.
- Atherosclerosis. The buildup of plaque that can damage the lining of a blood vessel is called Atherosclerosis. It increases the risk of an aneurysm.
- Male sex. Abdominal aortic aneurysms are much more common in men than women.
- Family history. An increased risk of AAA is seen in people who have a family member with abdominal aortic aneurysm. Also, aneurysms develop at a younger age and are at higher risk of rupture in people who have a family history of aneurysms.
Aneurysms of aorta are more common in the abdominal part of aorta. The exact cause of abdominal aortic aneurysms is unknown, but various factors may play a role, which include:
- Smoking. Both, cigarette smoking as well as chewing other forms of tobacco appears to increase the risk of aortic aneurysms. Additionally, smoking causes direct damage to the arteries, contributing to the buildup of fatty plaques in arteries (atherosclerosis) and high blood pressure. Aneurysms tend to increases in size faster in smokers, further increasing the risk of rupture.
- Hardened arteries (atherosclerosis). Risk of aneurysm increases when fat and other substances build up on the lining of a blood vessel (a process called atherosclerosis).
- Aortic wall infection (vasculitis). Abdominal aortic aneurysm, in rare instances, may be caused by an infection or inflammation that weakens a section of the aortic wall.
Abdominal aortic aneurysms are mostly slow growing and have no symptoms. This makes them difficult to detect. Some aneurysms will never rupture. Many aneurysms are small to begin with and stay small, although many expand over time. Some expand quickly. It is very difficult to predict how fast an abdominal aortic aneurysm may enlarge.
Enlargement of an abdominal aortic aneurysm may lead to:
- Feeling of pulsations around navel area
- Deep, constant pain in your abdomen or on the side of your abdomen
- Pain in back
Any person who is a smoker or aged 60 years or more, with a family history of abdominal aortic aneurysm is at risk of developing an abdominal aortic aneurysm. He/she should consider regular screening for the condition. As male sex as well as smoking has preponderance for abdominal aortic aneurysm, men ages 65 to 75 who have ever smoked cigarettes should have a one-time screening for abdominal aortic aneurysm using abdominal ultrasound.
Diagnosis of abdominal aortic is often by chance in patients presenting for examination for another disease. A pulsating bulge in abdomen may be felt by doctor during a routine exam. Aortic aneurysms are often found during routine medical tests. An X-ray of the chest or ultrasound of the heart or abdomen, sometimes ordered for a different reason, may lead to the diagnosis.
In case of high suspicion of an aortic aneurysm, the doctor may order specialized tests to confirm it. These tests might include:
- Abdominal ultrasound. An ultrasound examination of the abdomen can help diagnose an abdominal aortic aneurysm. It is a painless exam. The patient is asked to lie on back on an examination table and a small amount of warm gel is applied to the abdomen. The purpose of applying gel is to eliminate the formation of air pockets between your body and the instrument the doctor uses to see your aorta, called a transducer. The doctor presses the transducer against your skin over your abdomen, moving from one area to another. The images are sent to computer screen by the transducer which the doctor monitors to check for a potential aneurysm.
- Computerized tomography (CT) scan. This test is also a painless test that can provide the doctor with clear images of aorta. The patient, during a CT scan, is asked to lie on a table inside a doughnut-shaped machine called a gantry. Detectors inside the gantry measure the radiation that has passed through your body and converts it into electrical signals. These signals are gathered by a computer which assigns them a color ranging from black to white, depending on signal intensity. These images are assembled by the computer and it displays them on a computer monitor.
- Magnetic resonance imaging (MRI).This test is also a painless imaging test. Most MRI machines contain a large magnet shaped like a doughnut or tunnel. The patient lies on a movable table that slides into the tunnel. The atomic particles in some of your cells are aligned by the magnetic field. When radio waves are broadcast toward these aligned particles, they produce signals that vary according to the type of tissue they are. These images produced by the signals are used by doctors to see if the patient has an aneurysm or not.
Regular screening for people at risk of abdominal aortic aneurysms
Several medical bodies active in preventive medicine recommend that men aged 65 to 75 who have ever smoked should have a one-time screening for abdominal aortic aneurysm using abdominal ultrasound. The need for a screening ultrasound should be discussed with doctors by people older than age 60 with a family history of abdominal aortic aneurysm or other risk factors.
The main complication of abdominal aortic aneurysm is tears in the wall of the aorta (dissection). Life-threatening internal bleeding can ensue of an AAA ruptures. The risk of rupture is greater in large aneurysms.
Signs and symptoms indicating that aortic aneurysm has burst are:
- Onset of sudden, sharp and persistent abdominal or back pain
- Pain that radiates to your back or legs
- Increased sweating
- Cold and clammy skin
- Decreased blood pressure
- Rapid pulse
- Loss of consciousness
- Shortness of breath
Development of blood clots is another complication of aortic aneurysms. Small blood clots can develop in the area of the aortic aneurysm. A loose clot that breaks away from the wall of an aneurysm can block a blood vessel elsewhere in the body, causing pain or blocking the blood flow to the legs, toes, kidneys or abdominal organs.
Treatment of AAA is very specific. Some general guidelines for treating abdominal aortic aneurysms are:
In case of a patient having a small abdominal aortic aneurysm — about 1.6 inches, or 4 centimeters (cm), in diameter or smaller — and without symptoms, the doctor may suggest a watch-and-wait (observation) approach, rather than surgery. Surgery, in general, isn't needed for small aneurysms because the risk of surgery likely outweighs the risk of rupture. If a patient chooses the observation approach, the doctor will monitor the aneurysm with periodic ultrasounds, usually every six to 12 months and encourage the patient to report immediately if there is abdominal tenderness or back pain — potential signs of a dissection.
The size of a medium aneurysm is between 1.6 and 2.1 inches (4 and 5.3 cm). How the risks of surgery versus waiting stack up in the case of a medium-size abdominal aortic aneurysm, is unclear. The benefits and risks of waiting versus surgery will need to be discussed with the doctor and then an informed decision be made with the help of the doctor. In case of watchful waiting, an ultrasound will be needed every six to 12 months to monitor the aneurysm size.
Large, fast-growing or leaking aneurysm
Surgery is generally required in cases of an aneurysm that is large (larger than 2.2 inches, or 5.6 cm) or growing rapidly (grows more than 0.5 cm in six months). Additionally, a leaking, tender or painful aneurysm requires treatment.
For abdominal aortic aneurysms, two types of surgeries are available:
- Open-abdominal surgery is done to repair an abdominal aortic aneurysm. The surgery involves removing the damaged section of the aorta and replacing it with a synthetic tube (graft), which is sewn into place. This is done by opening the abdomen under naked eye. It generally takes a month or so to recover from this type of surgery.
- Endovascular surgery is a less invasive procedure. This type of surgery is sometimes used to repair an aneurysm. In this procedure, doctors attach a synthetic graft to the end of a thin tube (catheter) that's inserted through an artery in the leg and threaded up into the aorta. A woven tube covered by a metal mesh support — called as a graft - is placed at the site of the aneurysm and fastened in place with small hooks or pins. The purpose of placing a graft is to reinforce the weakened section of the aorta to prevent rupture of the aneurysm.
Patients undergoing endovascular surgery recover faster than those people who have undergone an open-abdominal surgery. But, due to more propensity of leakage from endovascular graft, follow-up appointments are more frequent. Follow-up ultrasounds are generally done every six months for the first year, and then once a year after that. Survival in the long run is similar for both endovascular surgery and open surgery.
Various factors will decide the treatment options for the aneurysm. These include location of the aneurysm, patient's age, kidney function and other conditions that may increase the risk of surgery or endovascular repair.
Lifestyle measures are the best approach to prevent an aortic aneurysm as they keep the blood vessels as healthy as possible. That means taking these steps:
- Quit smoking or chewing tobacco.
- Maintain a healthy blood pressure.
- Exercise regularly.
- Reduce intake of cholesterol and fat in your diet.
In case somebody has any of the risk factors for aortic aneurysm, it is very important to talk to the doctor. If you are at risk, your doctor may recommend additional measures. These include medications to lower blood pressure and relieve stress on weakened arteries.