What question did this study set out to answer?

To assess whether the urinary calcium-to-citrate ratio can differentiate stone-forming from non-stone-forming children under 24 months.

February 13, 2026Open Access

Urinary calcium-to-citrate ratio predicts kidney stone risk in children under the age of two years

Key Points

To assess whether the urinary calcium-to-citrate ratio can differentiate stone-forming from non-stone-forming children under 24 months.
Retrospective single-center study with 181 children aged 1-24 months.
Children underwent metabolic evaluation and ultrasonography for kidney stone diagnosis.
Participants categorized into normocalciuric stone-free controls, hypercalciuric stone-formers, and non-hypercalciuric stone-formers.
The calcium-to-citrate ratio was significantly higher in hypercalciuric stone-formers (0.46 mg/mg) than in controls (0.17 mg/mg).
A threshold of > 0.23 mg/mg for Ca/Cit showed moderate diagnostic ability (AUC 0.695).
Sensitivity reached 66.1% and specificity 63.2% for predicting stones in the evaluated age group.

Abstract

Abstract Background The urinary calcium-to-citrate (Ca/Cit) ratio has emerged as a useful indicator of lithogenic risk in older children; however, no reference data exist for infants and toddlers. This study aimed to evaluate whether the spot Ca/Cit ratio can distinguish stone-forming from non–stone-forming children under 24 months of age and to assess its diagnostic performance compared with conventional urinary markers. Methods This retrospective single-center study included 181 children aged 1–24 months who underwent metabolic evaluation and ultrasonography at their first presentation to a tertiary pediatric nephrology clinic between 2012 and 2024. Based on urinary calcium excretion and ultrasonographic findings, participants were categorized as normocalciuric stone-free controls ( n = 57), hypercalciuric stone-formers ( n = 29), or non-hypercalciuric stone-formers ( n = 95). Spot urine calcium, citrate, and related biochemical ratios were analyzed. The diagnostic accuracy of the Ca/Cit ratio for predicting stones was assessed using receiver operating characteristic (ROC) analysis. Results The Ca/Cit ratio differed significantly across groups, with the highest levels observed in hypercalciuric stone-formers (0.46 mg/mg) compared with controls (0.17 mg/mg; p 0.23 mg/mg (≈ 1.10 mmol/mmol) demonstrated moderate diagnostic ability for stone detection (AUC 0.695; 95% CI 0.613–0.785), yielding 66.1% sensitivity and 63.2% specificity. Age showed no meaningful correlation with Ca/Cit values. Normocalciuric stone-free children provided an age-appropriate reference distribution for Ca/Cit ratios. Conclusions In infants and toddlers evaluated for suspected urinary stone disease, the Ca/Cit ratio offers moderate discriminatory power and may serve as a practical adjunctive marker of stone risk. A ratio > 0.23 mg/mg (≈ 1.10 mmol/mmol) appears to indicate increased lithogenic potential. Larger prospective studies are needed to validate reference intervals and refine clinically applicable cut-off values for this young age group. Graphical Abstract

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Cite This Study

Dönger et al. (Wed,) studied this question.

synapsesocial.com/papers/698ebf9785a1ff6a93016f77 https://doi.org/https://doi.org/10.1007/s00467-026-07191-z

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