Our newly acquired 4 yr old 45lb dog just returned from vet - with urinary tract crystals & is now on a 2-month diet of Hill's Prescription Diet s/d canned food. Our vet suggested that a large percentage of dogs within a 50 mile radius of us have this same problem. She believes the local water supply may be a major contributor. After moving here about 2 years ago, I noticed strange heavy deposits in the bird baths and in the outside water dish (all filled from tap water). I never had this where we used to live. You may try giving your pet only bottled water along with the prescribed food. Also - ask your vet if you can eventually switch to a diet of cooked rice with some cooked mixed vegetables (no onions or seasonings). Our other dog has been on a diet of rice and vegetables with a small amount of chicken or high quality lamb/rice dry food and is doing very well. We are hoping we can eventually switch our new dog with the urinary tract problem to the rice/vegetable diet. One last suggestion from a local vet was add cranberry juice to your pet's water and to the food - as much as the pet can tolerate. Check with your vet and follow their direction. Good luck!