Abstract: Background – Hypercalciuria in calcium oxalate (CaOx) urolithiasis may be related to increased bone turnover. Objectives – To evaluate the urinary calcium excretion and bone turnover in dogs with CaOx urolithiasis. Animals – Breed- and age-matched dogs with CaOx stones (n=12) and non-stone formers (NF; n=12) were prospectively recruited. Dogs using calcium or vitamin D supplements were excluded. Methods – All dogs were fed commercial diets designed for struvite urolith dissolution and CaOx prevention. Fasting serum and urine samples were collected at two time-points (T1 and T2, with twenty days of interval) to perform the bone marker β-crosslaps (RI 0.36 – 2.50 ng/mL) and urine calcium-to-creatinine ratio (uCa:Cr; RI ≤ 0.05). Repeated measures two-way ANOVA was used for data analysis (P ≤ 0.05). Results – All dogs with CaOx urolithiasis had hypercalciuria, with higher uCa:Cr levels than NF at T1 (P= 0.0141). Until now, β-crosslaps have been assessed in seven dogs. CaOx group (n=4) showed 1.30 – 8.68; 1.91 ng/mL at T1, and 1.36 – 2.54; 1.53 ng/mL at T2; NF (n=3) had 0.44 –1.88; 1.27 ng/mL at T1, and 0.50 – 1.77; 0.58 ng/mL at T2. There was a trend towards β-crosslaps concentrations to be higher in CaOx group than NF. 2/4 dogs with CaOx urolithiasis showed hypercalciuria and high levels of β-crosslaps at least once. Conclusions and Clinical Importance – Dogs with CaOx and hypercalciuria may have increased bone turnover. Although preliminary, our results highlight the importance of assessing the extent of bone remodeling in hypercalciuric CaOx urolithiasis.
