Risk factors associated with struvite urolithiasis in dogs evaluated at general care veterinary hospitals in the United States

OBJECTIVE: To identify factors associated with development of struvite urolithiasis in dogs evaluated at general care veterinary hospitals in the United States. DESIGN: Retrospective case-control study. ANIMALS: 508 dogs with a first-time diagnosis of struvite urolithiasis and 7,135 control dogs. PROCEDURES: Electronic medical records of all dogs evaluated at 787 general care veterinary hospitals in the United States between October 2007 and December 2010 were reviewed to identify dogs that developed struvite urolithiasis and 2 groups of control dogs with no history of urolithiasis. Information extracted included diet, age, sex, neuter status, breed size category, hospital location, and date of diagnosis. Urinalysis results, urolith composition, and other disease conditions were recorded if applicable. Potential risk factors were assessed with univariable and multivariable regression analysis. RESULTS: Toy- or small-sized breeds had significantly greater odds of struvite urolithiasis, compared with medium- or large-sized breeds. Neutering significantly increased the odds of this outcome in females only; sexually intact females were more likely to develop struvite urolithiasis than were sexually intact males, but only up to 5 years of age. Urinary factors significantly associated with the outcome were basic (vs acidic) pH, presence of RBCs or WBCs, protein concentration > 30 mg/dL, and ketone concentration ≥ 5 mg/dL. CONCLUSIONS AND CLINICAL RELEVANCE: Evaluation of demographic characteristics and urinalysis results may be useful in the early identification of struvite urolithiasis in dogs. Periodic urinalysis in dogs is recommended because of the potential health impact of a late diagnosis of urolithiasis.