The pope underwent "a laparotomy and abdominal wall surgery under general anesthesia" on Wednesday, the Holy See's official news portal says. The pope had complained of abdominal pain on Tuesday.
The Ukrainian president held talks in Rome, where he received pledges of both open-ended military and financial support as well as stronger backing for Ukraine's aim to join the European Union.
Catholic women's groups that have long criticized the Vatican for treating women as second-class citizens immediately praised the move as historic in the 2,000-year life of the church.
Catch up on key developments and the latest in-depth coverage of Russia's invasion of Ukraine.
Pope Francis, hospitalized recently with bronchitis, skipped the procession because of cold weather. It was the first time a pope was a no-show at the Colosseum Way of the Cross procession since 2005.
Pope Francis opened the celebration Mass in St. Peter's Square on Palm Sunday, presiding at his first ceremony after his hospital stay for bronchitis.
Pope Francis was discharged from the Rome hospital where he was treated for bronchitis, quipping to journalists before being driven away: "I'm still alive."
The pope will leave the hospital on Saturday, three days after he was hospitalized for respiratory problems. He was diagnosed with bronchitis. Francis will be present for Palm Sunday ceremonies.
Vatican spokesman Matteo Bruni's second statement said that hospital tests showed Francis is suffering from a respiratory infection, but they ruled out COVID.
The leader of the world's 1.3 billion Catholics has steered his church leftward after more than two decades of conservative leadership. Opposition within the Vatican is fierce.
Pope Francis celebrated Mass before tens of thousands of people, to close out an unusual mission by Christian religious leaders to nudge forward the South Sudan's recovery from civil war.
While there is excitement, the trip comes with a sense of urgency. Despite a peace deal, violence along political and ethnic lines has continued and millions are in the grip of famine.
A rapturous reception as Pope Francis celebrates Mass with a million worshipers in the capital Kinshasa.
His trip to the Democratic Republic of Congo and South Sudan will highlight the long-running conflicts in both countries and the rising importance of Africa to the future of the Catholic Church.
He stressed that lack of charity with one another is also a sin and added that the Catholic Church should work to put an end to laws in some countries that criminalize homosexuality.