Pediatric GFR Calculator (Schwartz Equation)
Estimate kidney function in children using the Schwartz equation. Enter the child's height and serum creatinine to calculate eGFR and assess for chronic kidney disease.
Understanding Pediatric GFR
Glomerular filtration rate (GFR) measures how well the kidneys filter blood. In children, GFR estimation is more complex than in adults because muscle mass and creatinine production change rapidly with growth.
The Schwartz equation solves this by incorporating height, which correlates with muscle mass in children. The formula is eGFR = (0.413 × height in cm) / serum creatinine in mg/dL. The constant 0.413 is calibrated to standardized creatinine assays used since 2009.
A child's eGFR should be above 90 mL/min/1.73m² under normal conditions. Values below 60 for more than three months indicate chronic kidney disease. Below 15 signals kidney failure requiring dialysis or transplant preparation.
Medical disclaimer: This calculator is for educational purposes only. Pediatric kidney function assessment requires comprehensive evaluation by a pediatric nephrologist. Never diagnose or treat kidney disease in children based solely on this calculator.
Chronic Kidney Disease in Children
Chronic kidney disease (CKD) in children has different causes than in adults. Congenital abnormalities like kidney dysplasia, posterior urethral valves, and reflux nephropathy account for most cases. Hereditary diseases like polycystic kidney disease and Alport syndrome also occur.
CKD staging in children mirrors adults. Stage 1 (eGFR ≥90) and stage 2 (60-89) have normal or mildly reduced function but show kidney damage on imaging or urinalysis. Stage 3 (30-59) is moderate impairment. Stage 4 (15-29) is severe, and stage 5 (<15) is kidney failure.
Growth monitoring is critical in pediatric CKD. Kidney disease impairs growth hormone effectiveness, causing short stature. Children with eGFR below 60 need nutrition optimization, growth hormone if appropriate, and close height tracking.
Early detection and treatment preserve kidney function longer. Children with CKD need blood pressure control (often with ACE inhibitors), dietary protein and phosphate management, anemia treatment, and bone disease prevention. Specialized pediatric nephrology care improves outcomes significantly.
Interpreting eGFR Results in Children
An eGFR above 90 mL/min/1.73m² is reassuring but doesn't rule out kidney disease. Children can have structural kidney problems or early glomerular disease with preserved GFR. Always consider urinalysis, blood pressure, and imaging when assessing kidney health.
eGFR between 60-89 mL/min/1.73m² is mildly reduced. This may be normal in some children (especially infants under 2) but warrants investigation if persistent. Causes include mild reflux, resolved acute kidney injury, or early hereditary kidney disease.
eGFR below 60 mL/min/1.73m² lasting over three months defines chronic kidney disease. These children need referral to pediatric nephrology for workup, which may include kidney ultrasound, voiding cystourethrogram, genetic testing, or kidney biopsy.
Single abnormal results should be confirmed. Dehydration, illness, and certain medications (like NSAIDs) temporarily raise creatinine and lower calculated GFR. Repeat testing after adequate hydration and medication review ensures accurate assessment before labeling a child with chronic disease.
Frequently Asked Questions
What is the Schwartz equation?
The Schwartz equation estimates GFR in children using height and serum creatinine. The formula is eGFR = (k × height in cm) / creatinine in mg/dL, where k = 0.413 for children aged 1-18 years.
Why is height used instead of weight?
Height correlates with muscle mass and creatinine production in growing children better than weight. Using height makes the equation more accurate across different ages and body compositions.
What is a normal GFR in children?
Normal eGFR in children is above 90 mL/min/1.73m². Infants under 2 years have lower normal values (around 60-80) as kidneys mature. By age 2, GFR reaches adult levels.
When should I use the pediatric GFR calculator?
Use this for children aged 1-18 years. For infants under 1 year, different equations are needed. For adults (18+), use the CKD-EPI or MDRD equations instead.
How accurate is the Schwartz equation?
The Schwartz equation is accurate within 10-15% of measured GFR in most children. It's the standard screening tool for pediatric kidney disease but may be less accurate in very muscular or malnourished children.