Pope Francis "reacted well" to intenstinal surgery on Sunday evening at a hospital in Rome, the Vatican said.
He went into hospital for the planned operation just hours after cheerfully greeting the public in St. Peter’s Square, telling them he will go to Hungary and Slovakia in September.
The Vatican didn't give further information on his condition.
In a statement late on Sunday, a Holy See spokesman, Matteo Bruni, said the 84-year-old Francis had general anesthesia during the surgery necessitated by a narrowing of the large intestine.
The written statement, which came shortly before midnight, was notable for its scarcity of medical detail.
Bruni didn't say how long surgery lasted, nor for how long the pope was unconscious under anesthesia.
Also not immediately clear was how long Francis would stay at Rome's Agostino Gemelli Polyclinic, a Catholic hospital, although he was expected to convalesce for a few days in a private 10th floor apartment suite reserved for popes.
It was the pope's first known hospital treatment since he was elected to the papacy in 2013.
The Vatican said the 84-year-old pope had been diagnosed with “symptomatic diverticular stenosis of the colon,” a reference to a narrowing in the large intestine. The surgery was to be performed by Dr. Sergio Alfieri, the director of Gemelli's digestive surgery department.
A week earlier, Francis had used his same Sunday appearance to ask the public for special prayers for himself, which, in hindsight, might have hinted at the planned surgery.
“I ask you to pray for the pope, pray in a special way,” Francis had asked the faithful in the square on June 27. “The pope needs your prayers,” he said, adding his thanks and saying “I know you will do that.”
Francis is in generally good health, but did have part of one lung removed as a young man. He also suffers from sciatica, occasionally having painful bouts of the condition in which a nerve affects the lower back and leg. That has forced him at times to skip scheduled appearances.
The pope had a particularly demanding set of appointments last week, including celebrating a Mass on Tuesday to mark the Catholic feast day honoring Saints Peter and Paul, and later in the week, presiding at a special prayer service for Lebanon. On June 28, he also had a long private audience at the Vatican with U.S. Secretary of State Antony Blinken. Throughout all those engagements, Francis appeared to be in good spirits.
Gemelli doctors have performed surgery before on papal patients, including on Pope John Paul II, who had a benign tumor in his colon removed in 1992.