Bugged out
Very low phosphorous diet. This usually goes hand in hand with a lower protein diet, but pet food is messed up ( don't get me started), so you have to read every label carefully. I forget the percentage, but you can find it online or go to a really good pet store. If you can buy it at the grocery or a Walmart or Target, then I can promise you it is garbage. I don't even buy from Pet Smart or Petco any more because those foods are only minimally better and not good enough for a dog with health issues. Avoid anything from China. Avoid any brands that has had recalls (there are tons of them). Read the label EVERY TIME you buy a new bag of food. They change the ingredients and where it's manufactured ALL THE TIME. My dog is currently on Zignature Trout & Salmon. So far it's ok, but we've had to switch brands a few times in the past 2 years. If your vet recommends Hill's
Science Diet that they sell in their office FIND A NEW VET!!! It's seriously some of the worst pet food out there and I can't believe a "medical professional" would be pushing that crap. Up the green veggie intake. Steam or lightly boil plain broccoli, asparagus, kale, spinach and/or zucchini then run it through a food processor. Same concept as homemade baby food. Do not add anything to the veggies-- gotta be plain.
You can't reverse kidney damage in dogs. By the time it's diagnosed it's progressed too far. All you can do is not make it worse. Work on improving his diet and giving him lots of fresh filtered water and just take care of him and love him. Good luck!