JOHANNESBURG — South Africa's presidency says Nelson Mandela has undergone successful surgery to remove gallstones. The presidency said the 94-year-old Mandela underwent the surgery Saturday. The presidency said Mandela's doctors wanted to treat a recurrent lung infection before putting him through the surgery. The statement said: “The procedure was successful and Madiba is recovering.” It referred to Mandela by his clan name as a sign of affection. Mandela has been hospitalized since Dec. 8. — AP