When to Have Surgery After Being Diagnosed with an Abdominal Aortic Aneurysm (AAA)

Abdominal aortic aneurysms or AAA's as they are more commonly referred to, are a life-threatening condition. Aneurysms, an outpouching of the normal blood vessel (imagine a bubble on a tire) are caused by a weakness in the wall or lining of the vessel. The most common aneurysms are seen in the portion of the aorta just below the arteries to the kidneys.The aorta is the largest blood vessel of the body. Blood leaving the heart, travels via the aorta to the entire body to give oxygen to various tissues and organs for them to function properly. Aneurysms are life-threatening in that this weakness in the wall of the vessel make it prone to rupture causing massive internal bleeding and death. Once an aneurysm is discovered, it is recommended that it be repaired. You may be surprised to find that your doctor may not recommend repair right away and request that you be followed over time to watch for aneurysm growth.

While aneurysms are more likely to rupture than a normal blood vessel, the rate of rupture is still low until the aneurysm reaches a certain size, approximately 5 to 5.5cm. But more importantly, surgey to repair AAA's is a fairly major undertaking with a number of risks. Similar to fixing a plumbing leak by shutting off the main water valve, the blood flow above the aneurysm needs to be clamped off to repair the aneurysm. Stopping blood flow leads to deprivation of oxygen to tissues and organs below the aneurysm such as the kidneys and legs. In addition, clamping the aorta can strain the heart. Accordingly, potential complications of aneurysm surgery include development of a heart attack, a stroke, kidney failure, lung problems and death. The risk of complications is generally in the range of 1 to 5%. Existing health problems such as heart or lung disease can make the risk of developing complications higher. For example, if a person has pre-existing kidney problems, his or her kidneys would be more sensitive to reduced blood flow during repair of the aneurysm.

The risk of rupture of an AAA at sizes less than 5cm are generally less than the risk of repairing the AAA with open surgery and hence watchful waiting is advised.Surgeons are reluctant to put a person at a 1-5% risk of heart attack, stroke, or death when they have a 1-2% chance of aneurysm rupture. When the aneurysm reaches the size of 5 to 5.5cm, then the risk of rupture exceeds the risk of surgery, and surgery is advised. The one notable exception is if the aneurysm grows rapidly despite the size. If the aneurysm size increased greater than 0.5cm in six months or less, then surgery is recommended despite the original or final size of the aneurysm.

Source:
Ballard DJ, Filardo G, Fowkes G, Powell JT
Surgery for small asymptomatic abdominal aortic aneurysms.
Cochrane Database Syst Rev. 2008 Oct 8;(4):CD001835.