We lost both a dog and a cat to kidney failure, with similar symptoms, and the vet suggested anti-freeze was responsible but there isn't any around here.
Then I found similar problems could come from lily poisoning. And we did have 2 different lilies growing in the garden. Even in a vase, if puss brushes against it, gets pollen on her coat, then licks it off - that can be enough to kill her, which it did.
So I wish you well, but get rid of any lilies - kidney failure is a horrible way to go and very distressing for the family.
Robyn