Fasting Urinary Calcium‐to‐Creatinine and Oxalate‐to‐Creatinine Ratios in Dogs with Calcium Oxalate Urolithiasis and Breed‐Matched Controls

BACKGROUND: Hypercalciuria and hyperoxaluria are risk factors for calcium oxalate (CaOx) urolithiasis, but breed‐specific reports of urinary metabolites and their relationship with stone status are lacking. OBJECTIVE: To compare urinary metabolites (calcium and oxalate) and blood ionized calcium (iCa) concentrations between CaOx stone formers and breed‐matched stone‐free controls for the Miniature Schnauzer, Bichon Frise, and Shih Tzu breeds. ANIMALS: Forty‐seven Miniature Schnauzers (23 cases and 24 controls), 27 Bichons Frise (14 cases and 13 controls), and 15 Shih Tzus (7 cases and 8 controls). METHODS: Prospective study. Fasting spot urinary calcium‐to‐creatinine and oxalate‐to‐creatinine ratios (UCa/Cr and UOx/Cr, respectively) and blood iCa concentrations were measured and compared between cases and controls within and across breeds. Regression models were used to test the effect of patient and environmental factors on these variables. RESULTS: UCa/Cr was higher in cases than controls for each of the 3 breeds. In addition to stone status, being on a therapeutic food designed to prevent CaOx stone recurrence was associated with higher UCa/Cr. UOx/Cr did not differ between cases and controls for any of the breeds. Blood iCa was higher in cases than controls in the Miniature Schnauzer and Bichon Frise breeds and had a moderate correlation with UCa/Cr. CONCLUSIONS AND CLINICAL IMPORTANCE: Hypercalciuria is associated with CaOx stone status in the Miniature Schnauzer, Bichon Frise, and Shih Tzu breeds. UOx/Cr did not correlate with stone status in these 3 breeds. These findings may influence breed‐specific stone prevention recommendations.