One of my fosters is on Royal Canin SO and he loves it and has done fine on it! He had repeated stones and had to have three surgeries.
He is fine now and will always be on this food.
Hills does have good RX foods as well.
The only other option with pups with medical concerns like this is home cooking. I have cooked for a couple in the past. It is important that the diet be formulated by a vet nutritionist.
This web site is run by a vet nutritionist. She has an FAQ section and discusses all things dog nutrition related. She is awesome...and if you don't find a topic there that you are looking for, you can send her a message. She does respond!
www.petdiets.com