The Pope has been admitted to hospital for an operation on his intestine.
It comes a day after he had medical tests at a Rome hospital.
The Vatican said the procedure would be under general anaesthetic on Wednesday afternoon and he would stay in hospital for “some days”.
It said the 86-year-old had been suffering “recurrent, painful and worsening” symptoms caused by a incarcerated laparocele (abdominal hernia).
The Pope spent three days in hospital with a respiratory infection in March – joking “I’m still alive!” when he was discharged – and last month had to skip audiences because of a fever.
April – Pope Francis: ‘I’m still alive’
Two years ago, he also had 33cm (13 inches) of his colon removed because of an inflammation and narrowing of the large intestine.
He is also missing part of one lung, which was removed when he was a young man in Argentina, and often uses a cane to walk due to knee pain.
The Pope appeared in good spirits before he was admitted to hospital on Wednesday, using the Popemobile to greet people during his general audience in St Peter’s Square.
The Vatican said he was then taken to Rome’s Gemelli University Hospital for a “laparotomy and abdominal wall plastic surgery with prosthesis”.
A laparotomy involves a large incision in the abdomen to examine the organs and diagnose or treat any problems.
“The stay at the health facility will last several days to allow for the normal post-operative course and full functional recovery,” the Vatican said.
The Pope has a busy summer lined up, with a four-day trip to Portugal for World Youth Day at the start of August and a trip to Mongolia about four weeks later.