UPDATE: My dear Tony passed away in January 2015. In the last few months of his life, he suffered from diabetes and progressive liver failure. He lived a good long life, and I tried to manage his conditions with diet, but it reached a point when I just needed to feed him anything he would eat. I hope your cat lives well and healthy. I am updating this recipe with a few things I learned in the last couple of years.
My 15-year-old cat (Update 8/2014: Tony has just turned 18 years old!) has had kidney issues for a few years now. Over the last couple of years, I have managed it well by giving him homemade low-protein cat food made from recipes by established veterinary nutritionists, and under my vet's supervision. I choose not to buy the prescription canned food because of the numerous recalls that have plagued pet food in recent years, plus even though the food I make is expensive, it still costs less in the end than canned food, and I control the ingredients.
The process is time and labor intensive, but I use all parts of what I cook. I hope this is useful for you if you have an ailing cat as well. It may also be useful to you if you want to learn how to slow-cook chicken and use up all the parts of it.
DISCLAIMER: This is not meant to substitute for veterinary medical advice. It is a guide to how I prepare a recipe my vet recommended, along with other holistic wisdom I picked up along the way. Your mileage may vary, but please only proceed under medical supervision.