Struvite Crystals (Also posted in Food Group)

[Laurie, Wally & Charlotte]

For the past six months, Charlotte's pH has been fluctuating and she has had a number of urine tests with some showing struvite crystals and some without. An x-ray was taken in December and revealed no bladder stones. Our vet concluded that Charlotte's pH just goes up and down, and without any stones, this is Charlotte's "normal." About 10 days ago, she was showing physical signs of a UTI and was put on an antibiotic since we'd be traveling, but the urine evaluation did not find any bacteria. We have been flooding her food (Acana Grasslands) with water to dilute her urine, hoping that this will help keep the pH down. Next week, she'll have another x-ray done as well as a sterile urine culture. Here are my questions: If the x-ray shows no stone/s and the culture indicates no bacteria, but possibly struvite crystals again, should I change her food to one without starches (since starch alkalizes pH) and one without magnesium and calcium? Should I give her any supplements such as ascorbic acid, cranberries, d-mannose? Some of these are just for bacteria prevention if I understand it correctly. And if she doesn't have any bacteria in her urine, what would be the point? I'm hoping to find some additional perspectives to help inform our decisions moving forward. 

[Karen, Jasper and Jackdoodle]

I'm reposting my comment from your dicussion on this in The Food Group.

The cranberry supplements also make the urine more acidic, which is what you want with struvite crystals. 

I think that if there is no infection present (i.e. no bacteria), no stones, and she has no symptoms, a diet change isn't necessary. The crystals in themselves mean nothing; that can be genetic and runs in some Poodles, among other breeds. I'd continue to encourage more fluid intake and maybe increase animal protein in her diet if possible. You aren't going to find any commercial food with no starch at all, but you can try to reduce starch or grain intake by only giving 100% animal protein treats & chews, too. 
As F pointed out in the Food Group discussion, there are no commercial foods without magnesium and calcium, and dogs do need those minerals in their diets, even with urinary issues.