What MomTo4FemaleFelines said is what my vet said to me - that the pH determines the type of crystals and what should be done about them, and that wet food and plenty of water are the key. Smudge isn't a big fan of wet food, so I get [looks left and right] the kind that starts with T and mix in plenty of extra water along with his various medicines (skin & coat, Cosequin for his urinary tract, antihistamine for allergies, and fiber supplement) and he will eat that. I even got him a kitty water fountain - but he was afraid of it! Luckily he's much more enthusiastic about drinking out of a glass bowl in the living room than a steel one in the kitchen, and he's fine now.

Maybe the most important thing I did, although it was serendipitous, was put him on grain-free food (which I did because of his allergies). His crystals (struvite) were the kind that form when a cat's urinary pH is too high, and grain does drive up the pH. So between the Cosequin, which will also help keep his joints comfortable, and the grain-free food and extra water, he's quite the comfy kitty these days.

Love, Columbine