ArticlePediatric nephrology (Berlin, Germany)2026
Urinary calcium-to-citrate ratio predicts kidney stone risk in children under the age of two years.
Article in Pediatric nephrology (Berlin, Germany), 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
backgroundThe 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.
methodsThis 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.
resultsThe 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 < 0.001) and non-hypercalciuric stone-formers (0.31 mg/mg; p < 0.001). A Ca/Cit threshold > 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.
conclusionsIn 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.
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