Teddy had a UTI and struvite crystals. The crystals have to be dissolved or they will turn into bladder stones. We used a product called Uro-eze that we added to Teddy's food for several weeks to dissolve the crystals (and he also had a small stone). There is also a prescription diet from Hill's (it's called Hill's S/D). We did not use this product. You might want to ask your vet about Uro-eze. We found that it worked great, no side effects, not very expensive, and Teddy ate his regular home cooked food while on it.
BTW struvite crystals are not caused by food proteins - they are the result of a urinary tract infection. Your dog also needs an antibiotic. Urinary tract infections can be tough sometimes to clear so you might want to get a culture and sensitivity done as well to make sure you have the right antibiotic.
Hope this helps
