Pope Francis remains in critical condition, with blood tests showing mild signs of kidney failure “which is currently under control,” the Vatican said Sunday, as the 88-year-old pontiff battles pneumonia in both his lungs.

The pontiff's condition is touch-and-go, given his age, fragility and pre-existing lung disease, according to doctors.

The kidney ailment appears to be in an early stage, the Vatican said, adding that the pontiff is still receiving high flows of oxygen for his respiratory illness.