Canine Magnesium Ammonium Phosphate (Struvite) Uroliths

In most dogs struvite uroliths occur as a sequela to urinary tract infections with urease producing microbes.  Because of this, eradication or control of infections is the most important factor in preventing recurrence of most canine struvite uroliths.

Canine INFECTION-INDUCED Struvite Uroliths
  Urolith Dissolution

1. Prior to attempting dissolution, perform diagnostic studies to identify urolith size and location, as well as confirmation of urolith composition (urinalysis, radiography, analysis of retrieved stones, etc.).
2. Perform urine culture and susceptibility to identify bacterial pathogens (if present), and select appropriate antimicrobial therapy.  The fact that diuresis reduces the urine concentration of antimicrobic agents should be considered when formulating drug doses.
3. Administer appropriate antimicrobial agent; continue therapeutic doses of antimicrobics until there is radiographic evidence of complete dissolution.
4. Initiate therapy with a canned calculolytic diet that promotes acidic urine, diuresis, and is restricted in phosphorus and magnesium.
5. In general, we do not use urine acidifying drugs in our medical protocols for dissolution of infection-induced struvite uroliths.
6. Monitor response to therapy at appropriate intervals (every 2 to 4 weeks).  Uroliths dissolved in an average of 12 weeks in dogs with infection-induced struvite uroliths fed a struvitolytic diet in addition to appropriate antimicrobics.

     Minimizing Urolith Recurrence

1. Perform appropriate diagnostic studies to eradicate and control bacterial urinary tract infections.
2. Infection-induced struvite uroliths will not form in the absence of urease-positive microbial infections.

Canine STERILE Struvite Uroliths
  Urolith Dissolution

1. Prior to attempting dissolution, perform diagnostic studies to identify urolith size and location, as well as confirmation of urolith composition (urinalysis, radiography, analysis of retrieved stones, etc.).
2. Initiate therapy with a canned calculolytic diet that promotes acidic urine, diuresis, and is restricted in phosphorus and magnesium.
3. Monitor response to therapy at appropriate intervals (every 2 to 4 weeks).  Uroliths dissolved in an average of 5 to 6 weeks in dogs with sterile struvite uroliths fed a struvitolytic diet

 Minimizing Urolith Recurrence

1. Encourage additional water consumption or feed a canned diet to promote diuresis. 
2. Feed a maintenance diet that is restricted in magnesium and phosphorus and promotes acidic urine.
3. Use appropriate caution in dogs predisposed to calcium oxalate urolithiasis.

Early detection of small uroliths that recur despite appropriate medical therapy facilitates non-surgical removal by voiding urohydropropulsion.  Uroliths removed by voiding urohydropropulsion should be quantitatively analyzed.

All prevention recommendations should be adjusted to meet individual patient's needs.  We recommend follow-up urinalyses, serum chemistry profiles, and radiographs on a periodic basis.