Fister had UTI and was operated, so I know a bit about the problem. My vet says that what's important, is to give your cat food which only contain very little Magnesium, Calcium and Phosfor. Hills S/D will dissolve the crystals. Hills C/D is supposed to prevent them. So do look into that!

Of course, the more they drink, the better. Try putting a glass of water in a different place than next to the food bowl. That made Fister drink more. He has a glass in the corner of the bedroom. Also, after he got the drinkwell, his pee bisquits are bigger.