we just had to put down one of our cats earlier this year due to renal failure. He was about 10. We noticed that he lost alot of weight pretty quickly, he went from about 22-24# to about 15 when we finally noticed something was going on. (we had been trying to reduce his weight for quite a while and though we were finally successful...) But this cat used to drink a ton of water, then as he got worse he stopped drinking. We had to give him the fluids under the skin for a while. He wouldnt eat the renal food either. We just basically spoiled him for the last couple months, giving him plenty of wet food and treats so to keep him as hydrated as possible, but we made the decision early on that when we thought his quality of life was declining, we'd put him down. All you can do is just try to keep him hydrated and comfortable and enjoy him while hes still here. Its not fun watching anyone or anything die slowly.