Pediatric GFR Calculator | Bedside Schwartz eGFR

Schwartz 2009: eGFR (mL/min/1.73m²) = 0.413 × (height_cm / SCr_mg/dL). If creatinine is provided in µmol/L, we convert to mg/dL by dividing by 88.4.

Accurate height and creatinine units are critical. The 0.413 constant (k) was derived from children with CKD using IDMS‑traceable assays and is calibrated to estimate GFR normalized to a standard body surface area of 1.73m². The calculator assumes a stable serum creatinine and is most appropriate in children older than about 1 year with chronic or subacute kidney concerns rather than rapidly evolving acute kidney injury.

• Enter standing height in centimeters, measured without shoes and rounded to the nearest 0.5 cm.
• Enter serum creatinine from a recent lab draw, making sure the units on the report match the units selected in the calculator.
• The result is an estimate; it should be interpreted together with the child's history, exam, urine studies, and trends over time.

• Use in stable pediatric outpatients or inpatients when you need a quick estimate of kidney function to guide work‑up or medication dosing.
• Be cautious in settings of rapidly changing creatinine (acute kidney injury, sepsis, post‑contrast); measured GFR or serial labs are more informative.
• Values can be biased by extremes of muscle mass, malnutrition, or growth disorders—consider cystatin C or measured GFR when the estimate does not fit the clinical picture.
• Do not trend across different laboratories without confirming calibration; even small assay differences can shift eGFR by 10–20%.

eGFR estimates help stage kidney function, adjust renally cleared medications, and decide when to refer to nephrology.

• eGFR ≥ 90 mL/min/1.73m²: typically normal, but persistent proteinuria, hematuria, or structural anomalies still warrant evaluation.
• eGFR 60–89: mildly reduced; repeat labs, check blood pressure and urine protein, and monitor for progression.
• eGFR 30–59: moderate reduction; usually merits pediatric nephrology referral, medication review, and closer follow‑up.
• eGFR < 30: severe reduction; urgent specialist involvement, careful fluid/electrolyte management, and planning for long‑term kidney support.

In pediatrics, the same numeric cutoffs used for adult CKD staging are often applied, but decisions should always incorporate age, growth trajectory, blood pressure, and comorbidities rather than relying on eGFR alone.

1. Verify creatinine unit, assay consistency, and recent accurate height measurement.
2. Calculate eGFR and compare against prior trend instead of treating one value as definitive.
3. Pair result with urine findings, blood pressure, and medication list for dose-risk decisions.
4. If value is discordant with clinical picture, escalate to cystatin C or measured GFR pathways.
5. Document interpretation and follow-up interval so repeat testing is actionable.

Creatinine‑based eGFR formulas such as Schwartz 2009 were developed as practical tools to estimate kidney function without the complexity of inulin or radioisotope clearance studies. They are most reliable when creatinine is measured with standardized assays and when children have stable kidney function and typical muscle mass for age.

In children with very low or high muscle mass, recent changes in kidney function, or conditions that affect tubular secretion of creatinine, eGFR may substantially misrepresent true GFR. Cystatin C–based or combined equations, timed urine collections, or formal nuclear medicine GFR measurements may be more appropriate in these situations. Use the Schwartz estimate as one lens on kidney function rather than the sole determinant of diagnosis or treatment.

When you trend eGFR, keep laboratory methods, height measurement technique, and clinical events in mind. A small apparent change caused by assay differences or measurement error should not trigger the same response as a sustained, clinically consistent decline across multiple visits.

• Mixing creatinine units (umol/L vs mg/dL) across visits and misreading trend direction.
• Applying stable-CKD equations in rapidly evolving AKI without serial clinical reassessment.
• Ignoring muscle-mass extremes that can overestimate or underestimate true kidney function.
• Dose-adjusting high-risk medications from one unexpected value without confirmatory review.

• Rapid eGFR decline across serial checks with compatible clinical deterioration.
• AKI concern with unstable creatinine kinetics or oliguria despite seemingly preserved estimate.
• Major discordance between eGFR value and bedside assessment/urine findings.
• High-risk medication dosing decisions resting on a borderline or unexpected value.

• Current eGFR value, creatinine unit/source, and height measurement date.
• Trend direction compared with prior values and relevant urine/lab context.
• Medication dosing implications and adjustments made/pending.
• Escalation plan (cystatin C, measured GFR, nephrology referral) if needed.
• Planned reassessment interval and trigger for urgent reevaluation.

• New mild reduction without red flags: repeat creatinine/eGFR and urinalysis within 2-4 weeks to confirm trend direction.
• Moderate reduction or concerning urine/blood pressure findings: repeat labs within 3-7 days and align follow-up plan with nephrology access.
• Severe reduction, rapid decline, or clinical instability: same-day repeat/expanded workup and urgent specialist escalation.

• Do not renally dose high-risk medications from one unexpected value without checking recent trend and clinical context.
• If eGFR is near a dosing threshold, verify creatinine unit/lab source and consider confirmatory reassessment before major dose shifts.
• Document explicit follow-up timing whenever a dosing change is made on estimated kidney function.
• Escalate when estimate uncertainty is high (AKI concern, atypical muscle mass, discordant bedside findings).

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• Schwartz GJ, et al. JASN. 2009;20:629-637.
• Glomerular filtration rate estimation formulas for pediatric use (review)
• KDIGO: CKD evaluation and management guideline