I second that, always check with a vet first! One folk remedy that I heard of was to sprinkle some dried cranberries into their food. Cranberries and cranberry juice are great for human UTI's (I know from personal experience) - and we have a friend that mentioned that he uses the dried cranberry routine for his cats and they are all healthy.

Once again, I strongly caution that you should check with a vet first because I could be wrong.

good luck.