American Idol's Phillip Phillips In Urgent Need of Surgery

Multiple "Idol" sources tell us ... when Phillip went back home to Georgia last Saturday ... his family doctor spent almost the entire stay by his side and was alarmed by what he saw -- Phillip wasn't eating and looked horrible.

Phillip suffers from severe kidney problems and at the beginning of the competition it got so bad he had a stent put in as a temporary fix until he could have surgery. But the condition has worsened and Phillip's doc told him he needed surgery now. Phillip said he was not going to drop out of the show so the doctor told him he ABSOLUTELY had to go under the knife immediately after the finale.

We're told the recovery time for the surgery is at least 6 weeks.

Phillip's condition is taking its toll -- we're told the medication causes dry mouth, and it's had some impact on his singing.