(NEXSTAR) — Doctors revealed Sunday that blood tests for Pope Francis, the 88-year-old pontiff who has been hospitalized since Valentine's Day after a weeklong bout of bronchitis worsened, show early kidney failure.

Every day, roughly 360 people in the U.S. begin treatment (either dialysis or a transplant) for kidney failure, according to the Centers for Disease Control and Prevention. A patient is considered to be experiencing kidney failure if under 15 percent of their kidney is "working normally," the National Institute of Diabetes and Digestive and Kidney Diseases says.

Some of Pope Francis' blood tests showed “initial, mild, kidney failure,” but doctors said it was under control. The Vatican did not provide any details about Pope Francis' condition or what treatment, if any, he was receiving for his kidney failure.

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