Investigating 24-Hour Urine Expected Ranges of Non-Kidney Stone Formers: an EAU Endourology Research Group Systematic Review and Meta-Analysis
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Background and Objective
There is substantial variation in reference ranges for 24-hour urine collections, leading to diagnostic uncertainty. We aimed to curate robust evidence for expected ranges of 24-hour urine collections in the non-kidney stone forming population.
Methods
We performed a systematic review (PROSPERO ID: CRD42024590784) of healthy adults without kidney stone disease undergoing 24-hour urine collections. Each component was meta-analysed in R, stratified by age, sex and ancestry, meta-regression and sensitivity analyses for study design, collection completeness and bias. An explicit eight-branch decision framework selected the recommended analysis per component. Expected ranges were derived from the pooled SD (95% interval); evidence was quantified by GRADE.
Key Findings and Limitations
Seventy-two articles were included (10,284 participants). Expected ranges (mmol / 24 h unless stated): volume 1.0–2.5L, calcium 1.9–6.2, oxalate 0.2–0.6 (men) / 0.2–0.4 (women), urate 2.0–5.1(men)/2.3–3.5(women), pH 5.6–6.3, citrate 1.2–4.5, creatinine 12.2– 16.3(men)/7.2–12.6(women), phosphate 19–26, sodium 98–253, potassium 28–77, magnesium 3.1–4.8, ammonium 28–46(men)/20–40(women), chloride 84–218, sulphate 17–26(men)/7–30(women), urea 234–445. Principal limitations were: high between-study heterogeneity (I 2 >95% for most components) and assay/laboratory variability (most marked for citrate and potassium).
Conclusions and Clinical Implications
This is the first study to attempt a robust characterization of 24-hour urine expected ranges using meta-analysis. Six of the derived expected ranges (pH, oxalate, magnesium, sulphate, urate, creatinine) were broadly concordant with existing reference ranges, providing an evidence base for those specific components.
Take Home Message
This study establishes expected 24-hour urine values in a non-stone-forming population and provides empirical support for the derivation of reference ranges for several common urine analytes. I t also provides a repository of data for further analyses.
Patient summary
The existing 24-hour urine reference ranges are poorly characterised. These are important as they are used by clinicians to diagnose and guide treatment for conditions predisposing to kidney stone formation. We have robustly determined expected ranges for people without kidney stones after reviewing existing studies in more than 10,000 people. For several urine components the available data remain limited, and our ranges should be revisited as more evidence accumulates.
