I recently saw an ad put out by the Canadian Society of Vascular Surgeons (CSVS) calling for a national screening program for abdominal aortic aneurysm (AAA). AAA has been described as a ticking time bomb.
Now, not everybody knows where this ticking time bomb is sitting in our body. Please do not rush for a total body scan to look for this bomb and do not ask, “Doc, which wire should I pull to defuse the bomb, red or blue?” Just kidding.
Let me explain and dissect the three words: abdominal aortic aneurysm. As most of you know, abdomen is a space between the diaphragm and the pelvis. Aorta is the largest vessel in the body and runs from the heart to the pelvis. That means a segment of it passes through the abdomen. Word aneurysm is derived from Greek word aneurusma, which means to dilate. So, aneurysm is a sac like widening of an artery resulting from weakening of the artery wall.
The normal aortic width is approximately two centimeters in men and a bit smaller in women. As the aorta increases in size, the risk of rupture increases. The gradual increase in the size of the aorta occurs over several years and does not produce any symptoms. But when it ruptures and leaks the patient will develop pain in the abdomen. The clinical diagnosis is not easy but the rupture can be diagnosed with a CAT scan. Emergency surgery after a rupture does not always have a good outcome. The majority of the patients do not survive.
If AAA is detected early then elective surgery has a better outcome. Five per cent of men and under one per cent of women over the age of 65 have an AAA. It is the 10th leading cause of death in Canadian men older than age 65. Studies from the United Kingdom have shown screening programs for early detection and treatment of AAA are cost-effective and save lives.
CSVS makes the following recommendation:
-National and provincial health ministries develop a comprehensive population-based ultrasound screening program for AAA detection and referral.
-All men aged age 65-75 be screened for AAA
-Individual selective screening for those at high risk for AAA. For example: women over age 65 at high risk secondary to smoking, cerebro-vascular disease and family history of AAA and men less than 65 with positive family history.
What is required for screening? AAA can be visualized by just using simple ultrasound scan of the abdomen limited to visualization of the abdominal aorta. CSVS has reviewed data that demonstrated screening men 65 to 75 will reduce aneurysm related death by half and at seven year follow-up a benefit on all cause mortality was noted.
The data also shows three aneurysms discovered by screening and repaired electively, will prevent one aneurysm death. For men, the number needed to screen to prevent one AAA mortality is similar to mammography.
What about women? CSVS says the incidence of AAA in women is significantly less and population based screening in all women has not been shown to reduce mortality. Selective screening of women is recommended as discussed earlier.
In an interview in the Medical Post, Dr. Thomas Lindsay, a vascular surgeon and a spokesman for the CSVS says that elective surgical repair of AAA is considered when the aneurysm reaches a diameter of 5.5 cm. at which point the annual risk of rupture is in the neighborhood of 10 per cent. Persons with an enlarged aorta that hasn’t yet reached that diameter would need repeat ultrasound screenings every six months to two years.
About 1,000 Canadians suffer ruptured aortic aneurysms every year and most people die as a result. But doctors say they could cut that number in half with ultrasound screening programs.
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