Background Polymorphisms of the vitamin D receptor (VDR) are associated with calcium oxalate (CaOx) nephrolithiasis in humans. Objectives To investigate the association between VDR polymorphisms and susceptibility to CaOx urolithiasis in dogs. Animals Thirty‐five dogs with CaOx urolithiasis were compared with 40 stone‐free dogs. Methods This was a case‐control study. Two VDR gene polymorphisms (rs851998024 and rs852900542) were detected by specific TaqMan real‐time polymerase chain reaction assay, and their relationship with serum 1,25‐dihydroxyvitamin D, serum and urinary electrolyte concentrations was evaluated. Results The distribution of the rs852900542 polymorphism was significantly different between the case and the control dogs (x2 = 6.369, P = .04). Dogs with a CC or CT genotype had an increased risk of CaOx stones than those with the TT genotype (odds ratio = 3.82, 95% confidence interval 1.04‐13.98). The CaOx dogs with the TT genotype had a significantly lower urinary calcium‐to‐creatinine ratio than the CT+CC genotypes. 1,25‐(OH)2D concentrations did not differ between the cases and the controls (308.7 ± 217.4 vs 286.7 ± 185.1 pg/mL, P = .45). Conclusions and Clinical Importance This finding suggests that vitamin D metabolism might play a role in CaOx stone formation in dogs.

Background and Aim: Hypercalciuria is an important predisposing factor commonly found in humans and dogs with calcium oxalate (CaOx) urolithiasis. Calcium oxalate crystals can induce an inflammatory reaction that subsequently produces several proteins that have an inhibitory or stimulatory effect on stone formation. This study aimed to evaluate the differences in urinary proteomic profiles between hypercalciuric CaOx stone dogs and hypercalciuric stone-free dogs (CaOx stone and control groups, respectively). Materials and Methods: Seven dogs with hypercalciuric CaOx urolithiasis and breed-, sex-, and aged-matched controls with hypercalciuria were included in the study. Serum and urine samples were obtained from all dogs to analyze electrolytes. Urinary proteomic profiles were analyzed using liquid chromatography-mass spectrometry. Student's t-test was used to compare the differences between groups. Results: Forty-nine urinary proteins were identified in the stone-free and CaOx stone groups, whereas 19 and 6 proteins were unique in the CaOx stone and stone-free groups, respectively. The urinary thrombomodulin level was significantly higher in the CaOx stone group (relative ratio = 1.8, p < 0.01) than in the stone-free group. Conclusion: This study demonstrated that urinary proteomic profiles may be used as a candidate biomarker for urinary tract injury in CaOx urolithiasis in dogs.