Paediatric GFR Calculator (Revised Schwartz Formula)
Use this calculator to estimate Glomerular Filtration Rate (GFR) in children using the Revised Schwartz Formula.
Estimated GFR:
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The Glomerular Filtration Rate (GFR) is a crucial measure of kidney function, indicating how well the kidneys are filtering waste products from the blood. In children, accurately assessing GFR is vital for diagnosing and managing kidney diseases, monitoring treatment effectiveness, and adjusting medication dosages.
Why is GFR Measurement Important in Children?
- Early Detection: Identifying kidney dysfunction early can prevent or slow the progression of chronic kidney disease (CKD).
- Disease Management: GFR helps classify the stage of CKD and guides treatment strategies.
- Medication Dosing: Many medications are cleared by the kidneys, so accurate GFR is essential for safe and effective drug dosing in children.
- Monitoring Progression: Tracking GFR over time helps assess the stability or progression of kidney disease.
Challenges in Measuring GFR in Children
Direct measurement of GFR using exogenous markers (like inulin or iohexol clearance) is the gold standard but is often impractical, invasive, and expensive for routine clinical use, especially in children. Therefore, estimated GFR (eGFR) formulas are widely used.
The Revised Schwartz Formula
The Revised Schwartz Formula is one of the most commonly used equations to estimate GFR in children. It was developed to provide a more accurate estimation than previous formulas, particularly in diverse paediatric populations. The formula is:
GFR (mL/min/1.73m²) = 0.413 * Height (cm) / Serum Creatinine (mg/dL)
Where:
- 0.413: This is a constant derived from studies, representing the average k-coefficient for children.
- Height (cm): The child's height in centimeters. This is used as a surrogate for body surface area, which influences GFR.
- Serum Creatinine (mg/dL): The concentration of creatinine in the child's blood, measured in milligrams per deciliter. Creatinine is a waste product produced by muscle metabolism and is filtered by the kidneys.
Interpreting GFR Results in Children
Normal GFR values vary with age, especially in infants and young children, as kidney function matures. Generally, a GFR above 90 mL/min/1.73m² is considered normal for older children and adolescents. Lower values may indicate kidney impairment:
- GFR > 90 mL/min/1.73m²: Normal kidney function.
- GFR 60-89 mL/min/1.73m²: Mildly decreased kidney function (often considered Stage 2 CKD if there are other signs of kidney damage).
- GFR 30-59 mL/min/1.73m²: Moderately decreased kidney function (Stage 3 CKD).
- GFR 15-29 mL/min/1.73m²: Severely decreased kidney function (Stage 4 CKD).
- GFR < 15 mL/min/1.73m²: Kidney failure (Stage 5 CKD).
It's important to note that GFR estimates can be influenced by factors such as muscle mass, diet, and certain medications. A single GFR measurement should always be interpreted in the context of the child's overall clinical picture, age, and other laboratory findings. Consult with a healthcare professional for accurate diagnosis and treatment.
Examples of Paediatric GFR Calculation:
Example 1: Healthy Child
- Height: 120 cm
- Serum Creatinine: 0.5 mg/dL
- GFR = (0.413 * 120) / 0.5 = 99.12 mL/min/1.73m²
- Interpretation: This GFR is within the normal range for a child of this height.
Example 2: Younger Child
- Height: 80 cm
- Serum Creatinine: 0.3 mg/dL
- GFR = (0.413 * 80) / 0.3 = 109.90 mL/min/1.73m²
- Interpretation: This GFR is also within the normal range, reflecting healthy kidney function.
Example 3: Child with Potential Kidney Impairment
- Height: 150 cm
- Serum Creatinine: 1.2 mg/dL
- GFR = (0.413 * 150) / 1.2 = 51.63 mL/min/1.73m²
- Interpretation: This GFR suggests moderately decreased kidney function (Stage 3 CKD) and warrants further medical evaluation.
Disclaimer: This calculator provides an estimated GFR based on the Revised Schwartz Formula and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider for any health concerns.