Efficacy of medical dissolution for suspected struvite cystoliths in dogs

Background Medical dissolution of struvite uroliths in dogs is commonly recommended, but data on success rates and complications are limited. Objectives To evaluate the efficacy of medical dissolution for suspected struvite cystoliths in dogs. Animals Fifty client-owned dogs fed a therapeutic dissolution diet, with or without administration of antimicrobials, for treatment of suspected struvite cystoliths. Methods Single institution, retrospective case series. Medical records were reviewed for dogs with at least 1 follow-up visit. Dissolution success, complications, and possible predictors of success were evaluated. Results Full dissolution of cystoliths was achieved in 58% (29/50) of dogs within a median of 35 days (range, 13-167). Of 21 dogs without success, 7 each had partial dissolution, no dissolution, or undetermined outcome. Uroliths containing >10% nonstruvite mineral were common in the nonsuccess group (11/16 analyzed). Maximum urolith diameter, number of uroliths, and baseline urine pH did not differ significantly between dogs with and without success. Dissolution was more likely in dogs receiving antimicrobial therapy (OR = 16.3, 95% confidence interval 1.9-787.4, P = .002). Adverse events occurred in 9 dogs (18%); urethral obstructions were the most common, but 3 of 4 dogs with this complication were obstructed on presentation, before trial initiation. Conclusions and clinical importance Results support a medical dissolution trial for dogs with suspected struvite cystoliths. If no reduction in urolith size or number occurs by 1 month, a nonstruvite composition is likely, and alternative interventions should be considered. Dogs presenting with urethral obstructions should not be considered candidates for medical dissolution.