[anonymous]

I would go by your veterinarian’s recommendation. Your dog is a senior and has a medical condition that will not go away.
Outrageous ($$) is when the dog becomes very sick and you have to go to the emergency vet on a Sunday evening.
Some science based veterinary medicine here

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Homemade Diets for Cats and Dogs with Kidney Disease–Most Recipes are Wrong

Check the comments too. You can post a question if you wish, but the veterinarian cannot give you specific advice as he has not examined your dog.
Good luck
PS: There are no veterinarians here at DFA.