Wolflady, unfortunately, this is a question that still does not have a good answer. UTI's are a recurring problem in prone kitties, and males neutered young are particularly susceptible. Diet can definitely help, but it is no cure, and sometimes it doesn't even help. Some cats have to continually have their urethras flushed, and in extreme cases even the penis has to be removed (the narrow urethra cannot pass the large crystals and removing the penis removes the narrowest section of the urethra). You were wise to take him to the vet immediately because a completely blocked urethra can be fatal very quickly. Ask your vet what food he recommends. In most cases, it will not be a grocery store food, but if for financial reasons that's what you prefer, tell your vet that and he will recommend the best. Alot of vets concur that wet food is better than dry, too. Good luck with the little guy and watch him closely - if he starts straining again or begins to eliminate in inappropriate places, get him to the vet!