Ultrasound Screening for Abdominal Aortic Aneurysm

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The summary below is from the full report titled "Ultrasonographic Screening for Abdominal Aortic Aneurysms." It is in the 16 September 2003 issue of Annals of Internal Medicine (volume 139, pages 516-522). The author is F.A. Lederle.

What is the problem and what is known about it so far?

Abdominal aortic aneurysm (AAA) is a bulging of the main blood vessel in the abdominal area, which carries blood from the heart to the rest of the body. Aortic aneurysms are the 15th leading cause of death in the United States, occurring mostly among men older than 65 years of age and particularly in older men who smoke.

Although some patients may feel symptoms of AAAs, such as intense back or abdominal pain, most experience no symptoms. The aneurysm may grow until it bursts like a balloon. This bursting, or rupture, causes massive bleeding. Only 20% of patients survive rupture.

Physicians detect most AAAs during routine medical examination by feeling a mass in the abdomen that pulses with each heartbeat. Ultrasound is the preferred method of screening because it is accurate, well tolerated, and inexpensive. Surgery to prevent rupture consists of traditional open surgery, in which the abdomen is opened, the aneurysm removed, and a synthetic tube sewn in its place, or endovascular repair, a newer, less invasive procedure in which an expandable graft is inserted into the aneurysm.

Why did the author do this review?

Screening for AAAs has not become regular practice because the benefits compared with the risks and costs have been unclear. The author examined recent research to see whether the results justified AAA screening.

How did the author do this review?

The author identified AAA screening trials published in scientific journals since 1966 and consulted with the directors of these trials.

What did the author find?

Four large recent randomized trials of AAA screening showed a substantial reduction in AAA mortality, ranging from 21% to 68%. The data supported at least 1-time ultrasound screening for men 65 to 79 years of age who have ever smoked, with repair reserved for AAAs 5.5 cm or larger. In particular, 95% of all patients dying of AAA rupture are older than 65 years of age, and future death from AAA rupture is rare after a negative ultrasound at age 65 years. Cost data were not conclusive but supported the cost-effectiveness of routine AAA screening in men older than 65 years of age.

Most AAAs detected at screening were smaller than 5.5 cm; management of these small AAAs should include remeasurement with ultrasound every 6 months for AAAs 4.0 to 5.5 cm and every 2 to 3 years for smaller AAAs, with repair reserved for those that enlarge beyond 5.5 cm. Elective repair of AAAs smaller than 5.5 cm did not improve survival, even in good surgical candidates.

What are the implications of this review?

Mortality associated with AAA would be reduced by AAA screening, which remains uncommon in the United States. Currently, the U.S. Preventive Services Task Force does not endorse screening, and most health plans, including Medicare, do not cover it. The author suggests that if the Task Force recommended AAA screening, health plan coverage might follow.

On the other hand, screening would identify small AAAs unlikely to rupture in the patient's lifetime but would cause worry and risk from unnecessary procedures. In the United States, physicians frequently repair AAAs smaller than 5.5 cm, and elective repair results in 1 in 6 AAA-related deaths.