My 6 year old cat was just diagnosed with this today...so upset. She has been behaving normally and we only found out there was a problem by taking her in for a dental cleaning.
At first we were giving fluids every day. Sylvia was eating Iams food, and when I found out about the kidney disease I wanted to switch foods. I really dislike Science Diet due to the poor quality so I asked my vet if we HAD to use a prescription food. They said we could use any low protein/phosphorus food she will eat (she was very picky.) I did some research and got samples of a few foods, and found a good one she would eat, Wellness Lite. We switched to that and her kidney values began to improve with the fluids and the better food. After a while we went to fluids every other day, then 3x a week, then less. Sylvia's kidney values stayed normal or near normal for the next 2 years and we did not need to use any other medications. Unfortunately she developed mammary cancer which metastasized after surgery and we lost her to cancer after about 2-3 years from her renal failure diagnosis.