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

Abstract

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.

Keywords: CKD‐MBD; feline; hypercalcemia; mineralization; nephrolithiasis; radiology and diagnostic imaging; ultrasonography.

FIGURE 1

A CONSORT flow diagram of this prospective imaging study. (Created with BioRender.com)

FIGURE 2

Scatter plots illustrating the linear change of plasma (A) creatinine; (B) phosphate; (C) body weight; (D) ln[FGF23]; (E) ln[PTH]; (F) total calcium; and (G) ionized calcium in all enrolled cats in this prospective imaging study (n = 36) according to the classification of nephrocalcinosis determined by ultrasonography at enrolment (“absence of nephrocalcinosis” [crosses] vs “presence of nephrocalcinosis” [dots]) during the study period. The P‐value refers to the Group*Time interaction (as shown in Table 6) analyzed using linear mixed effects models, which assessed the difference in rate of change of the outcome variable between groups (“absence of nephrocalcinosis” vs “presence of nephrocalcinosis”) over time.