Struvite Dissolution Pearls for Veterinarians

Struvite (magnesium ammonium phosphate) bladder stones are a common stone seen in younger dogs. 99% of struvite stones are related to a urease-producing bacteria associated with a urinary tract infection. The great things about these stones are that they are completely dissolevable with medical therapy! Any patient that presents with bladder stones should have a urinalysis and urine culture. If the urine culture is positive, consider trying dissolution with a combination of antibiotics, a struvite dissolution diet, and periodic radiographs to monitor your progress.

Here are some pearls of wisdom when performing a struvite dissolution protocol:

1. Base your antibiotic therapy on a urine culture. The diet AND the antibiotics must be given throughout the dissolution protocol. Do not stop the antibiotics until you document that the stones are gone! The diet must be fed EXCLUSIVELY!
2. Once the stones are dissolved and the infection is resolved, these dogs do not need to stay on a stone prevention diet. This is an infection-related stone, so monitoring for infection is the most important preventive therapy.
3. It is a very small risk to develop a urinary obstruction as the stones get smaller in size. This is a RARE complication and should not be a reason not to attempt struvite dissolution.
4. Dogs with struvite stones who present with stranguria and hematuria often have these signs secondary to infection rather than the stones themselves. Once you treat the infection, you will often see a resolution in clinical signs.
5. Some of the dissolution diets are high in fat, so make sure there are no contraindications in your patients.

Learn more about the Internal Medicine Service at NorthStar VETS.

Kimberly Hammer, DVM, DACVIM – Medical Director, Robbinsville
Dr. Hammer received her veterinary degree from the University of Pennsylvania School of Veterinary Medicine in 2000. She spent a year at Mississippi State University College of Veterinary Medicine for a small animal internship and returned to the University of Pennsylvania for a two-year residency in small animal internal medicine. She earned board certification from the American College of Veterinary Internal Medicine in 2004. She has a special interest in interventional radiology/endoscopy and minimally invasive procedures. Her other interests include endocrinology, gastroenterology and hematology. She currently serves as the medical adviser for the NorthStar VETS blood bank. She joined the NorthStar VETS team in September 2007.