Srilanka, Feb. 25 -- Pope Francis is still critically ill as he battles double pneumonia, but his condition has shown a "slight improvement," the Vatican said Monday.The 88-year-old pontiff is spending his 11th night in Rome's Gemelli Hospital, making it the longest hospital stay of his nearly 12-year papacy.

"The clinical conditions of the Holy Father, in their critical nature, show a slight improvement," the health update read.

The pope, it said, was still receiving oxygen, "although with slightly reduced flow and oxygen percentage."

It added that the "mild kidney insufficiency," which was first reported on Sunday, was "not a cause for concern."

A Vatican official, who did not wish to be named because he was not authorized to speak...