The Risks of Abdominal Aortic Aneurysm
Lately, entrepreneurs have traveled from town to town offering to do screening examinations at a modest charge for several potentially serious conditions. These noninvasive tests typically use ultrasound to look for various forms of atherosclerosis or hardening of the arteries in the circulation to the brain, the abdomen and legs. The tests are sold to anyone willing to pay for them even if they are not at risk for the diseases. The problem with screening tests is that if they are done on people with a low probability of having the disease, there often tends to be too many false positives. Besides, looking for a test in someone not likely to have it is wasteful of resources, even if it's one's own money being spent.
Physicians depend on research studies to determine what groups are most likely to benefit from screening tests. Recently, the United States Preventive Services Task Force (USPSTF) has issued updated recommendations for screening for abdominal aortic aneurysm. The aorta is the main supply artery for the body, carrying all the blood from the heart to the organs below the neck. When atherosclerosis develops in the part of the aorta in the lower abdomen, it can weaken and develop a bulge called an aneurysm. This abdominal aortic aneurysm or AAA (sometimes called a "triple A") is a weak spot in the wall of the aorta which over time could leak or tear causing catastrophic blood loss and death. About 9,000 people die annually from ruptured abdominal aortic aneurysms.
AAA's can occur in people born with defective aortic walls. Most cases, however, arise in people with atherosclerosis, particularly those who smoke. Atherosclerosis is caused by high cholesterol, high blood pressure, and diabetes, but the greatest contributor by far is smoking. A person who has smoked more than a total of five packs of cigarettes in his or her lifetime is at increased risk. AAA occurs in men more than five times more frequently than in women and at an earlier age, though rarely under age 65. Rupture is unlikely under age 65 in men and 85 in women.
The risk of rupture of an AAA increases as the size exceeds 5 centimeters diameter (normal diameter is 2.5 centimeters or one inch). One year risk of rupture is 9 percent for diameters between 5 and 5.9 centimeters, 10 percent between 6 and 6.9 centimeters, and 33 percent for 7 centimeters and greater. While rupture is the most devastating complication, an AAA is often an obstruction to blood flow beyond the abdomen and can reduce circulation to the legs causing pain and poor healing.
Based on current research about the risk of development and rupture of an AAA, the USPSTF now recommends one time screening for AAA in men over 65 if they have ever smoked. Having other risk factors for atherosclerosis, such as, hypertension, diabetes, high cholesterol, known atherosclerosis in other parts of the body (coronary artery disease, stroke and so on), a family history of AAA and being tall add weight to the decision to screen.
Rupture in women is unlikely under age 85 and by that age, most women with AAA will have other diseases that make the risk of death from surgical repair of the AAA very high. In addition, women over 85 are likely to die from a disease other than AAA. For those reasons, screening of women is not recommended. It is believed that discovering and repairing an AAA in women is more likely to cause death and disability than leaving it alone. However, physicians have argued that the data showing reduced risk of rupture in women compared to men were obtained from British studies and that British women over the last 50 years did not smoke as much as American women. Consequently, some physicians will screen women at higher risk even though it is not recommended.
If no AAA is found at age 65, no further screening is needed since the risk of AAA developing after that is negligible. If an AAA less than 5 cm is found, it is reevaluated every six to 12 months to see if it enlarges. If it grows to a diameter over 5.4 cm or increases more than one cm per year, repair should be considered.
Traditional AAA repair involves cutting out the damaged part and replacing it with a Dacron graft. It is a major operation with a 4 - 5 percent mortality rate and a complication rate over 30 percent. A newer technique of endovascular repair in which a stent is placed inside the aorta has been used in recent years. While it has a lower mortality rate and does not involve an abdominal operation, it can not be used in all cases and long term success is unknown. Conversion of an endovascular repair to a traditional open repair has a 24 percent mortality rate.
What we know of AAA's and their complications sends a strong message: don't ever smoke; if you smoke, quit now. Clearly smoking is a risk that can be avoided. Any male over 65 who has been a smoker should be screened once for AAA. Women over 65, while not officially recommended for screening, should discuss their individual risk with their physicians to see if it is reasonable to screen them.
Some insurance plans do not pay for screening tests for AAA, including Medicare. The ultrasound test for AAA is quick and painless and costs between $50 and $100 and sometimes less depending on where the test is done. It should be done only by trained ultrasound technicians and interpreted only by qualified physicians, typically a vascular surgeon or radiologist.