Efficacy of two commercially available, low-magnesium, urine-acidifying dry foods for the dissolution of struvite uroliths in cats

J Am Vet Med Assoc. 2013 Oct 15;243(8):1147-53. doi: 10.2460/javma.243.8.1147.


Objective: To compare the efficacy and safety of using 2 commercially available, low-magnesium, urine-acidifying dry foods to dissolve sterile struvite uroliths in cats.

Design: Prospective, multicenter, randomized clinical trial .

Sample: 37 cats with presumed struvite uroliths.

Procedures: Cats were randomly assigned to be fed 1 of 2 low-magnesium, urine-acidifying dry foods (food A or B). For each cat, physical examination, urinalysis, and abdominal radiography were performed weekly to assess treatment response.

Results: 32 cats had complete urolith dissolution. Mean ± SD times for a 50% reduction in urolith size (0.69 ± 0.1 weeks) and complete urolith dissolution (13.0 ± 2.6 days) were significantly shorter for cats fed food A, compared with those (1.75 ± 0.27 weeks and 27.0 ± 2.6 days, respectively) for cats fed food B. At study termination, mean ± SD urine pH (6.083 ± 0.105) for cats fed food A was lower than that (6.431 ± 0.109) for cats fed food B. In 5 cats, uroliths did not dissolve and were subsequently determined to be composed of 100% ammonium urate (n = 4) or 100% calcium oxalate (1). Adverse events associated with diet were not observed in any of the cats.

Conclusions and clinical relevance: Results indicated that dietary dissolution is safe and effective for eradication of sterile struvite uroliths in cats. Cats fed food A had faster urolith dissolution than did cats fed food B. Lack of a reduction in urolith size at 2 weeks after diet initiation was indicative of misdiagnosis or noncompliance.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animal Feed / analysis*
  • Animals
  • Cat Diseases / diet therapy*
  • Cats
  • Diet / veterinary*
  • Female
  • Magnesium Compounds / chemistry*
  • Magnesium Compounds / urine
  • Male
  • Phosphates / chemistry*
  • Phosphates / urine
  • Struvite
  • Urolithiasis / diet therapy
  • Urolithiasis / veterinary*


  • Magnesium Compounds
  • Phosphates
  • Struvite