“Fifteen to 20 years ago, we didn’t see stones in the ureter,” says Dr. Berg. “Now we do.” One theory as to why has to do with the fact that one of the diets fed to dogs to treat struvite stones, the most common type of urinary stone there is in dogs, causes the urine to become more acidic. On one hand, that’s desirable because struvite stones, made of magnesium, ammonium, and phosphate, don’t form as easily in acidic urine as they do in alkaline urine. But a different type of stone — made of calcium oxalate and also quite common — does tend to form in acidic urine (and can’t be dissolved with diet). In other words, the anti-struvite stone diet may have increased the frequency of calcium oxalate stones. “We’re definitely seeing more of those now than we used to,” Dr. Berg says. “It’s thought that they form in the kidney and travel to the ureter, whereas struvite stones tend to form in the bladder, which is further down the urinary tract.” Cause-and-effect hasn’t been proven between diet and more stones in the ureter. But the association at this point is clear and warrants further investigation.
That said, many, many dogs are put on diets to dissolve struvite stones, and those diets are terrific, non-invasive therapies for a serious problem. Do not take your dog off an anti-struvite diet without consulting your veterinarian. Such a decision needs to be made on a dog-by-dog basis.