Pontiff shows signs of early kidney failure.

Pope Francis remains in a critical condition but had a "good" 10th night in hospital and slept well, the Vatican said on Monday.

"The night went well; the Pope slept and is resting," read the short statement issued by the Holy See press office.

The 88-year-old pontiff is entering his 11th day at Rome's Gemelli Hospital where he is being treated for double pneumonia and a complex lung infection.

On Sunday the Vatican said that blood tests revealed that the pope was suffering from "early, mild renal insufficiency, which is currently under control".

Despite being in a critical condition, the pontiff remained alert, responsive and attended Mass, according to the statement.

On Saturday Francis suffered a "prolonged asthma-like respiratory crisis" that required "high-flow" oxygen, the Vatican said, and he also received blood transfusions after tests revealed "thrombocytopenia, associated with anemia".

The Holy See added that the pontiff is "not out of danger" and that his "prognosis remains guarded."

In a post on X from his Pontifex account on Sunday, Pope Francis expressed his thanks for the "consoling prayers" from all over the world.

"I have recently received many messages of affections, and I have been particularly struck by the letters and drawings from children", the pope said.

On Sunday the Cardinal Vicar of Rome, Cardinal Baldo Reina, held a special Mass for Pope Francis at the Basilica of San Giovanni in Laterano, with prayer vigils taking place in St Peter's Square and outside the Gemelli Hospital.

The pope was admitted to the Gemelli on Friday 14 February after experiencing bronchitis and difficulties breathing for several days.

Photo credit: Riccardo De Luca - Update / Shutterstock.com.