My cat Spunky developed a UTI and the crystals and was put on Hills' s/d(I think). I do not like the Hills products becasue they have lots of junk in them(BHA, BHT, Ethyioun(SP)). I have a cat on the Royal Cannin Hypoallergenic diet, and I use their Indoor 27 as treats for the cats! When Spunky had the UTI, I do not think Royal Cannin was out there(that's how long ago!!). But besides the antiobiotic, the cat needs a special diet to help dissolve the crystals. I am surprised that you did not have to give sub q fluids. That was what the vet recommended(strongly)to get extra fluids in for a few days. Good luck with your kitty! Sandra