Pope Francis, who was admitted to hospital on Friday, will miss his usual public appearance and weekly prayer with pilgrims on Sunday, the Vatican has said.
Earlier, the Vatican said the pope would remain in hospital as long as necessary for his treatment.
Rome's largest hospital has a designed suite for popes, where it treated the late Pope John Paul II during his long papacy.
"Pope Francis has been updated on the many messages of closeness and affection received and expresses his gratitude, while asking that we continue to pray for him", the Vatican added.
The pope's tests showed some signs of improvement on Saturday and a slight fever had passed, it said, adding he had received communion and been praying, reading and resting.
