Kidney Stone 24-Hour Urine Risk Interpreter
Kidney Stone 24-Hour Urine Risk Interpreter
Read a 24-hour urine stone-risk panel against the European Association of Urology’s current limits: urine volume, calcium, oxalate, citrate, uric acid and pH, with sex-specific limits for citrate and uric acid. The page counts and lists every risk factor, says what each implies, and first checks the creatinine, because an incomplete collection fakes low results.
Which stone risk factors does this 24-hour urine show?
24-hour urine panel → risk factors flaggedA man of 80 kg with recurrent calcium oxalate stones. 24-hour urine: volume 1.6 L, creatinine 15 mmol, calcium 7.1, oxalate 0.46, citrate 1.5, uric acid 4.2 mmol, sodium 190 mmol, pH 5.8.
Six risk factors, each against the EAU limit
Collection check: creatinine 18–25 mg/kg/day (men), 15–20 (women); creatinine mg = mmol × 113.12
- EAU
- European Association of Urology guidelines on urolithiasis, 2026 edition, Table 4.2
- AUA
- American Urological Association 2014 guideline: sets a urine volume target of at least 2.5 L/day but no numeric limit for any analyte
- headline
- the number of the six factors flagged; each is listed with what it implies
Worked example
A man of 80 kg with recurrent calcium oxalate stones. 24-hour urine: volume 1.6 L, creatinine 15 mmol, calcium 7.1, oxalate 0.46, citrate 1.5, uric acid 4.2 mmol, sodium 190 mmol, pH 5.8.
Creatinine 15 mmol × 113.12 = 1,697 mg ÷ 80 kg = 21.2 mg/kg/day — inside 18 to 25, so the collection looks complete
Volume 1.6 is below 2.0 → flag · calcium 7.1 is above 5.0 → flag (below 8.0, the thiazide threshold)
Oxalate 0.46 is above 0.40 → flag · citrate 1.5 is below the male limit of 1.7 → flag
Uric acid 4.2 is not above the male limit of 5; pH 5.8 is between 5.5 and 6.2
4 of 6 flagged. Sodium 190 mmol/day implies about 11 g of salt, over twice the EAU ceiling
24-hour urine limits (EAU 2026, Table 4.2)
| Analyte | Men | Women | Note |
|---|---|---|---|
| Volume | Target 2.0–2.5 L/day | Same | AUA: at least 2.5 L/day |
| Calcium | 5.0 mmol/day reference; above 8.0 needs attention | Same | No sex difference in the EAU table |
| Oxalate | Above 0.40 confirms; above 0.5 enteric?; above 1.0 primary? | Same | — |
| Citrate | Below 1.7 mmol/day | Below 1.9 mmol/day | Sex-specific |
| Uric acid | Above 5 mmol/day | Above 4 mmol/day | Sex-specific |
| pH | Below 5.5 or above 6.2 | Same | Acidic arrest; RTA suspected |
| Creatinine | 18–25 mg/kg/day | 15–20 mg/kg/day | Collection completeness |
Reading the collection before reading the results
A 24-hour urine is the standard metabolic work-up after a recurrent kidney stone, or a first stone in someone at high risk. It measures the things that make urine more or less likely to crystallise: how dilute it is, how much calcium, oxalate and uric acid it carries, how much citrate is there to inhibit crystals, and its pH. Several are often abnormal at once, which is why this page counts and lists every flag instead of choosing one.
The limits come from the European Association of Urology’s urolithiasis guideline, 2026 edition. Two of them differ by sex: hypocitraturia is below 1.7 mmol a day in men and 1.9 in women, and hyperuricosuria is above 5 in men and 4 in women. The two major guidelines differ too, though less than is often assumed. The American Urological Association’s 2014 guideline, reaffirmed in 2019, tells clinicians which analytes to measure but sets no numeric limit for any of them; its one number is a urine volume of at least 2.5 litres a day, where the EAU aims for 2.0 to 2.5 litres. Reference laboratories in the United States publish their own sex-specific limits, which do not always match the EAU’s.
Before any of that, check the collection. A missed void lowers the volume and every daily total, so an under-collected urine fakes a low citrate and hides a high calcium or oxalate. Creatinine is excreted at a steady rate for a given muscle mass, and the EAU gives 18 to 25 mg/kg a day for men and 15 to 20 for women. Outside that range this page says so before it says anything else; the urine collection adequacy calculator does the same check in more detail. Spot ratios, such as the urine calcium-to-creatinine ratio calculator, are useful in children but do not replace a 24-hour collection in adults.
Treatment follows the flags: fluid for every stone former, salt and animal protein restriction for high calcium, thiazides above the EAU’s 8.0 mmol/day threshold, alkaline citrate for low citrate or acid urine, and dietary change or allopurinol for high uric acid. The stone’s composition, if known, matters as much as the urine. This page supports clinical judgement and does not replace it.
Frequently asked questions
What is a normal 24-hour urine calcium?
The EAU guideline’s reference is 5.0 mmol/day (about 200 mg), with more than 8.0 mmol/day (about 320 mg) needing medical attention. It gives no separate limits for men and women.
What urine volume should a stone former aim for?
The EAU targets 2.0 to 2.5 litres of urine a day; the AUA asks for at least 2.5 litres. Both mean drinking enough to make that much urine, which is usually more than 2.5 litres of fluid.
Why does the page check creatinine first?
Because an incomplete collection lowers every daily total. The creatinine output per kilogram shows whether the full 24 hours was collected; outside the expected range the results should be repeated before acting.
Which 24-hour urine limits differ between men and women?
In the EAU guideline, citrate (below 1.7 mmol/day in men, 1.9 in women is low) and uric acid (above 5 in men, 4 in women is high), and the expected creatinine output.
Related calculators
References
- European Association of Urology. EAU Guidelines on Urolithiasis, chapter 4: Metabolic evaluation and recurrence prevention, Table 4.2. EAU Guidelines Office, Arnhem; 2026 edition.
- Pearle MS, Goldfarb DS, Assimos DG, et al. Medical management of kidney stones: AUA guideline. J Urol. 2014;192(2):316–324. Validity confirmed 2019.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.