This version was machine-translated from German and has not been medically reviewed. The authoritative version is the German version.
Nephrology & urology
18 calculators · eGFR (Schwartz, CKiD U25), urine ratios, fractional excretions, AKI, bladder capacity
Here you will find calculators for pediatric nephrology and urology: eGFR according to bedside Schwartz 2009 and according to CKiD U25 (Pierce 2021) from creatinine, cystatin C or both, fractional excretions (FENa, FEUrea, FEUA, TRP, TmP/GFR) and urine ratios for protein, albumin and calcium. In addition there are the KDIGO AKI stages 2012, pRIFLE, expected bladder capacity according to ICCS, kidney length percentiles (Viteri 2025) as well as urine output and fluid balance. The calculators are intended for interpreting laboratory and sonography findings. Each calculator states its formula and sources.
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Kidney length percentiles
Sonographic kidney length and kidney volume by age and sex as percentiles (Viteri 2025) -
eGFR (bedside Schwartz 2009)
Estimated glomerular filtration rate from height and serum creatinine, with KDIGO categories -
eGFR by CKiD U25 (creatinine)
Age- and sex-dependent creatinine equation for 1–25-year-olds with chronic kidney disease (Pierce 2021) -
eGFR by CKiD U25 (cystatin C)
Cystatin C equation for 1–25-year-olds: eGFR = K / cystatin C with age- and sex-dependent K -
eGFR by CKiD U25 (creatinine + cystatin C)
Mean of the creatinine and cystatin C estimates – the most accurate variant of the CKiD U25 equations -
FENa – fractional sodium excretion
Prerenal (< 1 %) or intrinsic (≥ 3 %)? From sodium and creatinine in urine and serum -
FEUrea – fractional urea excretion
More reliable than FENa under diuretics: ≤ 35 % suggests prerenal kidney failure -
FEUA – fractional uric acid excretion
In hyponatremia: SIADH and salt loss show FEUA > 11 %; normal 4–11 % -
TRP – tubular phosphate reabsorption
From phosphate and creatinine in urine and serum – normal approximately 85–95 % -
TmP/GFR – renal phosphate threshold
According to Payne from TRP and serum phosphate, with reference range by age and sex (1–73 years) -
Protein/creatinine ratio in spot urine
Normal ≤ 0.2 mg/mg (from 2 years) or ≤ 0.5 mg/mg (6–24 months); nephrotic ≥ 2 mg/mg -
Albumin/creatinine ratio (ACR)
KDIGO albuminuria categories A1 (< 30 mg/g), A2 (30–300 mg/g), A3 (> 300 mg/g) -
Calcium/creatinine ratio in spot urine
Hypercalciuria screening with age-specific P95 values (Sargent 1993): < 7 months 0.86, 7–18 months 0.60, 19 months to 6 years 0.42, from 7 years 0.22 mg/mg -
Expected bladder capacity (EBC)
ICCS formula 30 × (age + 1) ml with assessment of the maximum voided volume; Koff and Kaefer formulas for comparison -
pRIFLE – acute kidney injury in children
Risk / Injury / Failure from the decline in estimated creatinine clearance and urine output (Akcan-Arikan 2007) -
KDIGO AKI stages
Stage 1–3 based on creatinine rise (relative and absolute), urine output, renal replacement therapy and eGFR < 35 in children -
Urine output and fluid balance
ml/kg/h with KDIGO oliguria stage and balance in ml, ml/kg and % of body weight -
Renal Angina Index (RAI): risk of severe kidney injury in the pediatric intensive care unit
Risk × injury (fall in creatinine clearance or fluid overload) on the day of admission, 1–40 points; from 8 there is a risk of severe AKI on day 3 (Basu 2014)
Frequently asked questions
Which eGFR formula for children?
The eGFR (bedside Schwartz 2009) calculator uses height and IDMS-calibrated creatinine. The eGFR according to CKiD U25 (Pierce 2021) is available with creatinine, with cystatin C or as the mean of both estimates.
How do I distinguish prerenal kidney failure from acute tubular necrosis?
The FENa calculator computes the fractional sodium excretion to differentiate prerenal kidney failure (below 1 %) from acute tubular necrosis. FEUrea complements this: ≤ 35 % suggests prerenal kidney failure.
How do I stage acute kidney injury?
The KDIGO AKI stages calculator stages according to KDIGO 2012 based on serum creatinine. In children, pRIFLE is also available, which assesses the decrease in estimated creatinine clearance. Both state their sources.