RALEIGH, N.C. -- As a former smoker with a history of heart disease, Vice President Dick Cheney, 64, is a prime candidate for problems with weakened arteries called aneurysms.

During a routine physical exam in July, the vice president's doctors discovered popliteal aneurysms behind both of his knees, reported WRAL-TV in Raleigh.

While Cheney is expected to undergo surgery this weekend for an aneurysm behind his right knee, left untreated, an aneurysm -- a ballooning of a weak spot in the artery -- could cause serious problems.

"It's much more common in men," said Dr. George Clark, a vascular surgeon in Raleigh. "Much more common in male smokers, usually after age 60 to 65."

Ultrasound and angiogram images offer the best way to diagnose the condition.

Whereas the vice president's aneurysms are behind his knees, Clark said they are more common in the aorta in the abdomen and are more likely to burst and cause death. Popliteal aneurysms, like Cheney's, typically do not burst.

One potential complication of a popliteal aneurysm is the formation of blood clots, which could break away and block blood flow to the lower leg, causing pain and possibly the loss of the foot.

One way to fix the problem is with a stent graft placed within the weakened artery. Through an arterial opening near the groin, surgeons thread a catheter to the aneurysm and place a stent graft inside the artery. It removes pressure to the aneurysm and restores normal blood flow.

"If you can imagine an aneurysm, which is an enlarged blood vessel, kind of like my finger, you're going to go right inside there, getting into a normal-sized blood vessel above and a normal-sized blood vessel below," Clark said.

The most common fix, however, is through open surgery, where surgeons take a vein from an arm or leg to graft around the aneurysm and redirect blood flow, bypassing the aneurysm.

The White House has not given details about which procedure Cheney will undergo, but his hospital stay is expected to be short and he should recover quickly.