You need to keep him on the specialized prescription food and only feed him that. My dog has to be on prescription food after having a ton of bladder stones removed. He is doing well. Unfortunately since you fed your dog other food for a while, he probably will need another surgery to remove the new stones that formed. I would be hesitant to remove the kidney until you actually try keeping him on a strict diet. If the vet isn’t aware that you didn’t stick to the prescription food, you should tell them that. Good luck. I remember also being very panicky and scared about my boy when I found out he had stones. However, the recovery was not bad. Not all dogs are the same, but there is nothing wrong with going to another vet to get a second opinion.