Pope Francis has "reacted well" to planned intestinal surgery on Sunday evening at a Rome hospital, the Vatican said.
Holy See spokesman Matteo Bruni said the 84-year-old Francis's surgery was necessitated by a narrowing of the large intestine.
The written statement, which came shortly before midnight, was notable for its scarcity of medical detail.
Mr Bruni did not say how long surgery lasted, nor for how long the pope was under general anaesthetic.
Also not immediately clear is how long Francis would stay Rome's Agostino Gemelli Polyclinic, a Catholic hospital, although he is expected to convalesce for a few days in a private 10th floor apartment suite reserved for popes.
"The Holy Father, admitted in the afternoon to A Gemelli Polyclinic, underwent in the evening planned surgery for a diverticular stenosis of the sigmoid (portion of the colon)", Mr Bruni said in the brief written statement.
"The Holy Father reacted well to the surgery conducted under general anaesthesia," the spokesman said, noting there was a four-person surgical team, plus a four-person anaesthesiologist team.
A stenosis is an abnormal constriction or narrowing. The sigmoid portion of the large intestine extends from the end of the descending colon to the rectum.
Gastroenterologists say the sigmoid segment is a common location for a diverticular stenosis.
The main surgeon was Dr Sergio Alfieri, the director of Gemelli's digestive surgery department.
Among those present in the operating room was the official papal physician.
The pope's previous physician had contracted Covid-19 and died at Gemelli while undergoing cancer treatment.
It was a remarkable end to a day that began publicly for Francis when, during his traditional Sunday appearance to the faithful in St Peter's Square, he cheerfully announced he would go to Hungary and Slovakia in September.
The pope made no mention of his impending surgery, but headed to the hospital shortly after his window appearance.
At the end of his public remarks from an Apostolic Palace window, Francis told the crowd: "And please, don't forget to pray for me."
Then he added, sounding casual, almost wistfully: "Thanks, ciao."
A couple hours after he was admitted, reportedly arriving with little escort and no fanfare, the Vatican revealed that Francis had been diagnosed with a narrowing in the large intestine.
A week earlier, Francis had used his same Sunday appearance to ask the public for special prayers for himself, which may have been related to 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."
A diverticulum is pouch-like protrusion through the muscular wall of the intestine.
When diverticula become inflamed - a common condition, especially in older people - part of the intestine can sometimes narrow and surgery might be required, according to gastroenterologists.
Such surgery can be performed under general anaesthetic, possibly with a laparoscopic intervention.
Sometimes a re-sectioning of the affected part of the intestine is needed.
Francis is in generally good health, but he did have part of one lung removed as a young man. He also suffers from sciatica, in which a nerve affects the lower back and leg, a painful condition 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 honouring 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 US secretary of state Antony Blinken. Throughout all those engagements, Francis appeared to be in good spirits.
Get-well wishes began arriving immediately for Francis. Italian president Sergio Mattarella, as soon as he landed in Paris for a state visit in France, offered an "affectionate thought" on behalf of all Italians.
Mr Mattarella said he was wishing for "a good convalescence and even a speedier recovery" for the pope.
Gemelli doctors have performed surgery before on popes, notably Pope John Paul II, who had what the Vatican said was a benign tumour in his colon removed in 1992.
John Paul had several other surgeries at the hospital, including after being shot by a gunman in St Peter's Square in 1981.
After those surgeries, the Vatican and hospital officials gave detailed accounts of the pope's medical condition.
John Paul also had several medical issues in his final years, including severe complications from Parkinson's disease, and had numerous stays at Gemelli.
At one point, the future St John Paul II dubbed the hospital "the third Vatican", after Vatican City and the papal summer residence at Castel Gandolfo outside Rome.