Last May my English Springer Spaniel (1.5 yrs old)had surgery to remove Calcium Oxalates (Bladder Stones). He was prescribed a diet of Hills U/D. Not only does he hate this dog food, but it also makes him very constipated. He will only go to the bathroom at MOST 1 time a day, but usually every other day. When he does finally go poop, he strains so hard, and his stool comes out in small spheres that are hard as rock. I have tried adding water, olive oil, pumpkin, and rice (obviously not all at the same time), and he always has water available. Nothing seems to help loosen his stool. I have asked my Vet if there is another type of food that could be prescribed...they have told me "No." I do not believe that. I refuse to believe that Hills is the only dog food company out there that ONLY makes a prescription diet for dogs that are prone to developing bladde stones. I believe the food is supposed to change the acidity of the urine, so the bladder stones can't form. Is there anyone who has information on this topic? It would be greatly appreciated.