For the Nutritional Management of Dogs with Urinary Tract Disease Associated with Struvite. Urinary tract disease is associated with the build-up of crystals and stones in the urinary tract that can cause painful and bloody urination and potential blockage in your dog. One type of crystal that forms in a dog's urinary tract is called struvite. Prescription Diet c/d dog food is formulated specifically to provide nutritional management of dogs with struvite-related urinary tract disease. Prescription Diet c/d has reduced levels of magnesium and phosphorus, and also produces an acid urine pH to aid in the management of struvite crystals and stones. The nutritional formulation of Prescription Diet c/d may also be useful for pets with a variety of conditions.