Here is a homemade renal diet that I will use for kidney failure cats. I will also use Marrow soup, the recipe has been posted here previously. Let me know if I need to post that as well.

1/4 cup cooked chicken breast
1/2 ounce clams, canned, chopped in juice
1/4 cup rice, long-grain, cooked or sweet potato or pumpkin
1 Tablespoon chicken fat
1/8 teaspoon salt substitute-potassium chloride
1 calcium carbonate tablet (400 milligrams calcium)
1 250mg taurine tablet
1 cat multivitamin (liquid or powder)

You can omit the clams as long as you use the taurine tablets. I would put this into a food processor and process until smooth. You can also add egg whites if you desire.