Save my baby boy thanos

About a week ago we had start to notice Thanos losing muscle mass from not eating as much as normal we had assumed it was because we just moved and he was just down in the dumps. After taking him to the vet they said we needed to take him to the animal hospital because his kidneys were having trouble and they wanted to monitor him overnight. For a 2 day stay and the test they are gonna run is going to cost me every thing I have. I still have to wait to figure out what the treatment will be if there will be one but I'm at the end of my rope and I didn't know where else to go. Anything will help I just don't want to lose my baby boy he means alot to me anyone who knows me knows this. He is currently at dovelewis animal hospital in Portland Oregon and we are waiting to here back about testing still. If you can help anyway please do.