Bill Clinton faces surgery on Thursday to remove scar tissue and a build-up of fluid in his chest in a low-risk procedure doctors say is rarely necessary as a follow-up to the heart surgery the former president had last year.

Surgery for Clinton, 58, was set to begin on Thursday morning and last one to three hours, said his doctors at New York-Presbyterian Hospital, where he underwent quadruple heart bypass surgery last September.

Clinton arrived at the hospital by car before dawn without speaking to waiting reporters.

He is expected to remain hospitalized from three to 10 days but to make a full recovery, the doctors said.

The procedure, called a decortication, is common and “relatively low-risk” but rarely done as a follow-up to bypass surgery, doctors said. It requires general anesthesia.

Dr. Craig Smith, chief of the hospital’s division of cardio-thoracic surgery, said in some 6,000 cases of bypass surgery like Clinton’s, he had seen fewer than 10 cases that required the follow-up surgery.

“This is the extremely unusual end result of an extremely common process,” Smith said at a news conference on Tuesday.

Clinton has been suffering from a condition called a pleural effusion, in which scar tissue has caused fluid to build up around and compress his left lung. It has caused him shortness of breath while exercising and some chest discomfort, doctors said.

During the surgery doctors planned to remove the thick scar tissue over his lung and drain the built-up fluid.

Following news of the surgery, Clinton told reporters: “I feel fine ... It’s a routine sort of deal… no big deal. I’m in good shape.”

Doctors said Clinton, who served eight years in the White House from 1993 until 2001, recently passed a stress test “with flying colors.”

He recently traveled across Asia with former President George H. W. Bush to review aid operations following the tsunami disaster in the region.

Doctors said Clinton’s activities had not contributed to his need for the surgery. The former president knew before his trip that he would need to undergo the procedure, they said.

At the time of his bypass, doctors said Clinton would have risked a “substantial” Heart attack without surgery because some of his arteries were 90 percent blocked.