Former U.S. President Bill Clinton was released from the hospital on Monday, four days after surgery to remove fluid and scar tissue that accumulated in his chest after his heart-bypass operation last year.

Clinton, 58, left New York-Presbyterian Hospital. He had checked in on Thursday for a follow-up procedure to his quadruple heart-bypass surgery in September.

“Hillary, Chelsea and I are very grateful to the medical team that cared for me at the hospital and we deeply appreciate all the prayers and good wishes we’ve received in recent days,” Clinton said in a statement issued by his spokesman.

The procedure, called a decortication, was described by his doctors as low-risk, although the condition is rarely seen in heart-bypass patients.

Thoracic surgeon Joshua Sonett, who performed the operation, described the scar tissue on Clinton’s lung as like a “large thick rind” and said the procedure was “like peeling an orange.”

The condition had caused some compression on the former president’s left lung, left him short of breath while exercising and gave him some chest discomfort.

Clinton is expected to recuperate in his home in Chappaqua, New York. The normal recovery time is four to six weeks, doctors said.