I don't have experience with kidney failure, but I had a look in the archives here (I put "dog kidney failure diet" into the search box, and a few older posts came up. I have not had time to read them all, but this one might be helpful:
http://www.medhelp.org/posts/Dogs/excessive-thirst-and-peeing-in-house/show/736354
You could check out those old posts, see if you can find anything there to help. With kidney failure I gather that the situation is the lost kidney function does not return. BUT it is possible with careful management, to slow down the degenerative process to a great extent, and keep whatever kidney function your dog has, right now, for a time, at least.