For the Nutritional Management of Pets with Struvite Related Feline Lower Urinary Tract Disease (FLUTD) FLUTD is a problem often involving the formation of mineral-based crystals and stones in your cat's urinary tract that can cause a variety of painful symptoms, including obstruction. Struvite and oxalate are the two most common crystals that form in a cat's urinary tract. Prescription Diet s/d was developed to provide nutritional management of cats with struvite-related FLUTD. Struvite crystals and stones form as a result of urine that is over-burdened with magnesium, ammonium and phosphorus as well as an alkaline urinary pH. ONLY AVAILABLE IN AUSTRALIA - QLD, NSW, VIC AND ACT