Blood Work

The aneurysms that were detected behind each of Vice President Dick Cheney's knees during a routine checkup this summer are not necessarily anything to get alarmed about. An aneurysm is a ballooning of a blood vessel, similar to a bulge in an inner tube. You hear about it most often when it appears in the brain or heart, where, if it bursts, it is often fatal. But an aneurysm can show up anywhere in the body where there are blood vessels, including the popliteal artery that runs behind the knee.

Popliteal aneurysms don't usually burst and are safer than most. But doctors take them seriously because they can form blood clots. Sometimes a piece of a clot will break off and travel to the small blood vessels in the foot, causing something called blue-toe syndrome. A larger clot, however, may block blood flow below the knee completely. This is a serious medical condition; half the patients who get it will lose a leg.

What doctors look at is the size of the aneurysm, says Dr. K. Craig Kent, chief of vascular surgery at New York--Presbyterian Hospital. Bulges smaller than 2 cm (0.8 in.) in diameter can be left alone unless they grow bigger, at which point most vascular surgeons will recommend treatment. The standard approach is to tie off the affected blood vessel and create a bypass. A newer, less invasive procedure involves inserting a catheter in the artery of the groin and threading a small cylindrical mesh called a stent to the site of the aneurysm. The stent shores up the walls of the blood vessel and greatly reduces the risk of a clot. For patients who have trouble tolerating general anesthesia, the less invasive approach can be performed under local anesthesia, with a short hospital stay.

Luckily, popliteal aneurysms are rare--and rarely fatal. If you have one, however, you are likely to have others elsewhere in your body. According to Dr. Kent, the Vice President should be regularly screened for an abdominal aortic aneurysm, a dilation of the major vessel that funnels blood away from the heart. The U.S. Preventive Services Task Force takes it a step further and recommends screening for any man ages 65 to 75 who has ever smoked. o

Sanjay Gupta is a neurosurgeon and CNN medical correspondent