Quite often, kidney blood values can be high, esp creatinine, when infection and/or dehydration is present. Thats what happened with my cat Sam recently, he had to have a tooth removed and it had got infected. The bloods showed his creatinine levels quite high, but my vet pointed out that it was lliely due to the infection and a bit of dehydration too. I expect his levels will return to normal now the infection is under control. I had noticed he was drinking quite a bit prior to the dental - which is why I wanted full bloods done prior to the extraction, but he's not drinking so much now.
He was such a trooper - only hours after the op, he had his normal dinner like nothing happened