If the cat has kidney problems you must not feed it extra protein. My Mishi has a weak kidney and is on a special low-protein prescription kidney diet food. And, yes, they do get kinda peaked looking. It may not be bad purrenting, but just the way cats with kidney problems look. Mishi sometimes looks thin and his fur looks all funky, even though he's on the right diet and gets regular grooming, it's just a fact of life dealing with kidney disease. We love them for as long as they're with us.