Risk factors and implications associated with ultrasound-diagnosed nephrocalcinosis in cats with chronic kidney disease

Background: Microscopic nephrocalcinosis is a common pathological feature of chronic kidney disease (CKD) in cats. Detection of macroscopic nephrocalcinosis using ultrasonography and its implications remain unexplored. Objectives: Identify risk factors associated with ultrasound-diagnosed nephrocalcinosis and evaluate the influence of nephrocalcinosis on CKD progression. Animals: Thirty-six euthyroid client-owned cats with CKD. Methods: Prospective cohort study. Cats with CKD with and without ionized hypercalcemia were enrolled for renal ultrasonography. Cats were categorized according to the presence or absence of ultrasound-diagnosed nephrocalcinosis. Binary logistic regression was performed to identify nephrocalcinosis risk factors. The influence of nephrocalcinosis on CKD progression was assessed using linear mixed models. Results: Ultrasound-diagnosed nephrocalcinosis was evident in 61% of CKD cats overall, with increased prevalence (81%) in those with hypercalcemia. At enrollment, higher blood ionized calcium concentration (odds ratio [OR], 1.27 per 0.1 mg/dL; P =.01), plasma phosphate concentration (OR, 1.16 per 0.1 mg/dL; P =.05), plasma creatinine concentration (OR, 1.29 per 0.1 mg/dL; P =.02) and alanine aminotransferase activity (OR, 2.08 per 10 U/L; P =.04) were independent nephrocalcinosis risk factors. The rate of change in log-transformed fibroblast growth factor-23 differed significantly between groups (P =.04). Cats with CKD and nephrocalcinosis had increasing plasma creatinine concentrations (.03 ±.01 mg/dL/month; P =.04) and phosphate concentrations (.06 ±.02 mg/dL/month; P <.001) and decreasing body weight (.02 ±.01 kg/month; P <.001) over time. Conclusions and Clinical Importance: Nephrocalcinosis is prevalent in cats with CKD, especially in those with hypercalcemia. This pathological feature appears to be associated with CKD progression in cats.