Former U.S. President Jimmy Carter has liver surgery

ATLANTA, Aug. 4 (UPI) -- Former U.S. President Jimmy Carter underwent surgery to remove a mass in his liver Monday.

Emory University Hospital issued a statement saying his operation "proceeded without issues" and that he is due for a "full recovery." It is unkown if Carter remains in the hospital.

Carter, 90 , is the second-oldest living U.S. president behind George H.W. Bush, who is about four months older. Bush dealt with a broken neck vertebra in July.

Carter's surgery follows the publication of his book, "A Full Life: Reflections at 90," which was described by a reviewer as a warm memoir of Carter's youth alongside an assessment of the issues he tackled as the 39th president of the United States. He was recently spotted in Austin, Texas signing copies of his new book.

In his retirement, Carter has maintained good health and traveled regularly. So far this year he has visited places in the Middle East and South America, although he cut a May trip to Guyana short due to feeling ill.