Bill Clinton's (search) latest medical problem is an unusual but not ominous complication of heart surgery, and the procedure to fix it is not particularly risky, experts say.

"It's a less-than-1-percent risk of anything major happening to him," said Dr. W. Randolph Chitwood of East Carolina University (search), a spokesman for the American College of Cardiology. "He should do fine."

On Thursday, the former president, who underwent quadruple bypass surgery (search) in September, will have fluid drained from his chest and scar tissue removed from the surface of his left lung. He will stay in the hospital for three to 10 days, his office says.

Heart surgery patients occasionally develop a fluid buildup in the chest that presses on the lungs. Often the body absorbs the fluid, or doctors can draw it off with a tube.

But in Clinton's case, the fluid has spurred the body into forming scar tissue on the surface of his left lung. So even after the fluid is removed, the scar mass would keep the lung from expanding fully when he inhales, said Dr. Eugene Grossi of the New York University School of Medicine.

The condition can cause pain while inhaling and make a person short of breath because the lung can't fully function, he said. Clinton's office said the lower lobe of his left lung collapsed, giving him "some discomfort in recent weeks."

So Clinton, 58, has been scheduled for a procedure called a decortication, something only about 2 percent to 3 percent of heart surgery patients require.

Using either a small incision or a sort of surgical telescope inserted between the ribs, surgeons will drain fluid and scrape and peel the scar tissue off the lung.

The procedure is a tedious job, which involves removing the scar tissue without cutting the lung itself, said heart surgeon Dr. Joseph DeRose of St. Luke's-Roosevelt Hospital in New York. It typically takes about one to two hours, he said.

After the procedure is done, surgeons leave a tube in the chest to drain off any further fluid as well as air escaping from any small nicks in the lung. The tube is kept in for several days, depending on how much fluid is still coming out and how quickly the lung heals, experts said.