- Enter the measured urine volume in mL collected during a defined interval.
- Enter the collection interval (and choose hours or minutes). Leaving the interval at 1 hour lets you type a straight mL/hr value into the volume field.
- Enter the child's weight in kilograms and pick the correct age category (neonate <28 days · infant 1 mo–1 yr · toddler/child 1–12 yr · adolescent ≥12 yr).
- The calculator returns the rate in mL/kg/hr and classifies it as anuria, oliguria, normal, or polyuria against age-banded thresholds.
All computation runs in your browser; no values are stored or transmitted.
When to Use
Use this calculator whenever you need to translate a measured urine volume in a child into a weight- and age-normalized rate and decide whether the output is anuric, oliguric, normal, or polyuric. Because pediatric thresholds differ from adult values and shift across the first decade of life, expressing output in mL/kg/hr and comparing it against the age band is the foundation of pediatric AKI surveillance and fluid management.
Appropriate population
Hospitalized neonates, infants, children, and adolescents with a reliable urine collection (indwelling catheter or weighed diapers) — especially those at AKI risk (sepsis, post-cardiac surgery, nephrotoxin exposure, hypovolemia, obstruction) or being monitored after fluid resuscitation. Also useful for screening polyuria (diabetes insipidus, diuretic phase of recovering AKI, post-obstructive diuresis, osmotic diuresis).
When NOT to rely on it
An accurate rate requires an accurately measured volume over a defined interval and a recent dry weight. Diaper weights without a baseline, intermittent voids in a non-catheterized child, and very short collection windows give noisy estimates. Non-oliguric AKI is common in critically ill children — a "normal" rate does not rule out AKI, and creatinine-based criteria still apply. Diuretics, glycosuria, and high osmolar loads inflate urine output independent of true GFR.
Pearls & Pitfalls
Age bands matter
Normal urine output is highest in neonates (1–3 mL/kg/hr), still high in infants (1–2 mL/kg/hr), and drops toward adult values in older children and adolescents (0.5–1 mL/kg/hr). Oliguria in an adolescent is <0.5 mL/kg/hr; in a neonate the same number would be frankly anuric. Always classify against the correct age band before acting.
pRIFLE / pKDIGO link
Sustained oliguria (<0.5 mL/kg/hr for ≥8 h, or progressively longer intervals) is the urine-output arm of the pRIFLE and pediatric KDIGO AKI definitions. Pair every borderline rate with a serum creatinine trend — many children meet AKI by creatinine before they cross the urine-output threshold, and a normal rate alone does not exclude AKI.
Pitfalls
(1) Weighed diapers require a dry-diaper baseline and prompt weighing to avoid evaporative loss. (2) Sweating, vomiting, NG losses, and insensible losses are not captured — a low rate may reflect prerenal hypovolemia, not intrinsic AKI. (3) A urinary catheter that is obstructed or kinked masquerades as oliguria — always rule out a mechanical cause before escalating. (4) Polyuria (>~4 mL/kg/hr) warrants its own workup — diabetes insipidus, hyperglycemia, recovering AKI, post-obstructive diuresis, or osmotic load from contrast or mannitol. (5) Fluid overload can mask oliguric AKI when output is "adequate" only because intake is excessive.
Why Use It
Urine output is the simplest bedside marker of renal perfusion and is the only piece of the AKI definition that updates in real time, but raw mL totals are misleading in pediatrics: a 60 mL/h output is excellent for a 50 kg adolescent and frankly polyuric for a 5 kg infant. Converting volume to a weight- and age-normalized rate, and then comparing that rate against the band appropriate for the child's age, lets the clinician escalate care for oliguria, recognize polyuria that demands its own workup, and document the urine-output arm of the pRIFLE / pediatric KDIGO criteria reliably and reproducibly.
Pediatric Urine Output Rate
Enter urine volume, collection interval, weight, and age category to get the rate in mL/kg/hr and the age-banded classification (anuria · oliguria · normal · polyuria).
⚕ KDIGO AKI 2012 · Akcan-Arikan A et al. Kidney Int. 2007 (pRIFLE) · Sutherland SM et al. CJASN. 2013. Age-banded urine-output thresholds underlie the pRIFLE / pediatric KDIGO definitions of AKI. Accuracy depends on reliable urine collection (indwelling catheter or weighed diapers) and a recent dry weight. Non-oliguric AKI is common — interpret alongside the serum creatinine trend and clinical context. For licensed clinicians; not a substitute for individualized assessment.
Next Steps
Use the age-banded rate to direct the next move.
- Anuria (essentially 0 mL/kg/hr): rule out a mechanical cause first (catheter obstruction, kinked drain, retention). Address shock, obstruction, and nephrotoxic exposures; obtain renal ultrasound; check serum creatinine and electrolytes; escalate to pediatric AKI staging and consider early nephrology consultation.
- Oliguria (below the age-band threshold): assess volume status and perfusion, treat hypovolemia with cautious isotonic fluid resuscitation (avoid aggressive boluses in cardiac or fluid-overloaded children), review nephrotoxins, and trend creatinine to stage AKI by pRIFLE / pediatric KDIGO.
- Normal range: reassuring for the urine-output arm of the AKI definition but does not exclude non-oliguric AKI — continue creatinine surveillance in at-risk children.
- Polyuria (>~4 mL/kg/hr): work up diabetes insipidus, hyperglycemia, recovering or diuretic-phase AKI, post-obstructive diuresis, and osmotic loads (contrast, mannitol). Match urinary losses with appropriate fluid and electrolyte replacement.
- Cross-link: pair the rate with the Renal Angina Index and pediatric AKI staging tools for risk stratification and definitional staging.
Evidence & References
Formula
| Quantity | Formula |
|---|---|
| UO rate (mL/kg/hr) | urine volume (mL) ÷ collection interval (hr) ÷ weight (kg) |
| Interval conversion | minutes ÷ 60 = hours |
| Polyuria threshold (pediatric, generic) | > ~4 mL/kg/hr |
Age-banded Normal & Oliguria Thresholds
| Age band | Normal (mL/kg/hr) | Oliguria threshold |
|---|---|---|
| Neonate (<28 days) | 1 – 3 | < 1.0 mL/kg/hr (anuria essentially 0) |
| Infant (1 mo – 1 yr) | 1 – 2 | < 1.0 mL/kg/hr |
| Toddler / Child (1 – 12 yr) | 0.5 – 1.5 | < 1.0 mL/kg/hr (conservative) |
| Adolescent (≥12 yr) | 0.5 – 1.0 | < 0.5 mL/kg/hr |
Pediatric AKI definitions (pRIFLE, pediatric KDIGO) incorporate urine-output thresholds (commonly <0.5 mL/kg/hr sustained over progressively longer intervals) alongside serum creatinine and eGFR changes. Accurate measurement (indwelling catheter or weighed diapers with a dry baseline) and a recent dry weight are essential for valid interpretation.
References
- KDIGO AKI Work Group. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Int Suppl. 2012;2(1):1–138.
- Akcan-Arikan A, Zappitelli M, Loftis LL, Washburn KK, Jefferson LS, Goldstein SL. Modified RIFLE criteria in critically ill children with acute kidney injury. Kidney Int. 2007;71(10):1028–1035.
- Sutherland SM, Byrnes JJ, Kothari M, et al. AKI in hospitalized children: comparing the pRIFLE, AKIN, and KDIGO definitions. Clin J Am Soc Nephrol. 2013;8(10):1661–1669.
