Abstract

Objective: This study investigated the impact of 24-hour urinary calcium excretion (UCaE) on renal function decline in hospitalized patients with and without chronic kidney disease (CKD).

Methods: This study enrolled 3,815 CKD patients with stages 1-4, and 1,133 Non-CKD patients admitted to the First Center of the Chinese PLA General Hospital between January 2014 and July 2022. The primary outcome for CKD was a composite of CKD progression defined as a 40% decline in estimated glomerular filtration rate (eGFR) and end-stage kidney disease and rapid kidney function decline [RKFD, defined as annual eGFR decline of ≥ 5 ml/min/1.73m ²/yr] as the secondary outcome. For Non-CKD patients, an eGFR decline of ≥ 20%, incidence of CKD, and a declining slope of ≥3 ml/min/1.73m ²/yr were the outcomes. The association between UCaE and kidney function decline was assessed using Cox proportional hazards and generalized linear models.

Results: The primary outcome was observed in 813 CKD and 109 without CKD over a median follow-up of 3.0 and 4.1 years, respectively. For CKD patients, every 1-mmol/d increase in UCaE was associated with a 15% decreased risk of CKD progression. The hazard ratio (HR) was 0.85, with a 95% confidence interval (CI) of 0.77-0.93. And, for Non-CKD patients, the risk of renal function decline decreased by 11%. The multivariate models indicated that there was an annual decrease of eGFR in both CKD and Non-CKD, with a reduction of 0.122 ml/min/1.73m2/yr (P < 0.001) and 0.046 ml/min/1.73m2/yr (P = 0.004), respectively, for every 1-mmol/d increase of UCaE.

Conclusions: CKD experiences a decrease in 24-hour UCaE as early as stage 1, with a significant decline in stage 4. CKD and Non-CKD patients with lower UCaE levels are at an increased risk of renal decline, regardless of other variables.