Pope Francis remained in critical condition Sunday and blood tests show early kidney failure but he remains alert and “well-oriented,” and attended Mass, the Vatican said, as the 88-year-old pontiff battles pneumonia and a complex lung infection.

Pope Francis appears to have an "early, mild renal insufficiency" as he remains hospitalized in critical condition, the Holy See Press Office said in Sunday evening update.

Pope Francis remains in critical condition and on oxygen therapy after a "respiratory crisis" the night before. NBC News' Claudio Lavanga reports on the latest.