My Sheltie is also in early stages of renal disease. We caught it early with a blood test and at this time he has no symptoms, so his illness may be less advanced than Casey's. We decided to pursue an alternative protocol with a high-quality, moderate protein, lots-of-water (no kibble) diet and so far he is doing well. Blood work 2 months after the change in diet showed marginal improvement. We'll repeat in August to see where he is. My guy is also 13. You may want to check out Barbara Royal's book, "The Royal Treatment" and others for alternative points of view, although if your guy is doing well you might not want to mess with success. Best of luck with Casey. We love them to pieces.