Hello my dog was just diagnosed also. Although my dog has already been on K/D prescription diet. That is what the vet recommended. My dog has basically not eaten for a week. I have had to syringe feed her, until yesterday she is a different dog and wants everything. I don't really have an answer about food but I got baby food(no onions) get the meat stuff and she ate it up. Then the next day I mixed the baby food with the K/D and she ate that up.
I have been giving her fluids SubQ's which is important. I also ordered some vitamins. Baby food is not good long term because it is high in phosphorus but it was a start to get my dog to eat, along with the fluids. I've joined a group called K9kidneys on yahoo and it has been great with advice.
I am still learning but I think that a prepared diet is the best. I am just learning but human foods low in protein and phosperous are the best. Good luck and my heart is with you and I know what you are going through.