U25 GFR Calculator

CKiD U25 Equation:

\[ eGFR = 39.8 \times (Height / Scr)^{0.456} \times (1.8 / Scys)^{0.418} \times (30 / BUN)^{0.079} \times (1.076 \text{ if male}) \times (Height / 1.4)^{0.179} \]

Height:

Serum Creatinine (Scr):

mg/dL

Serum Cystatin C (Scys):

mg/L

Blood Urea Nitrogen (BUN):

mg/dL

Gender:

Estimated GFR (eGFR):

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1. What is the CKiD U25 Equation?

The CKiD U25 (Chronic Kidney Disease in Children Under 25) equation estimates glomerular filtration rate (GFR) specifically for pediatric and young adult populations aged 1-25 years. It incorporates height, serum creatinine, cystatin C, BUN, and gender to provide accurate kidney function assessment in younger populations.

2. How Does the Calculator Work?

The calculator uses the CKiD U25 equation:

\[ eGFR = 39.8 \times (Height / Scr)^{0.456} \times (1.8 / Scys)^{0.418} \times (30 / BUN)^{0.079} \times (1.076 \text{ if male}) \times (Height / 1.4)^{0.179} \]

Where:

\( Height \) — Height in meters
\( Scr \) — Serum creatinine (mg/dL)
\( Scys \) — Serum cystatin C (mg/L)
\( BUN \) — Blood urea nitrogen (mg/dL)
1.076 — Male multiplier

Explanation: This equation is specifically validated for pediatric and young adult populations and accounts for growth-related changes in kidney function.

3. Importance of eGFR Calculation in Pediatrics

Details: Accurate GFR estimation in children and young adults is essential for diagnosing kidney disease, monitoring growth and development, and adjusting medication dosages appropriately for age and body size.

4. Using the Calculator

Tips: Enter height in meters, serum creatinine in mg/dL, cystatin C in mg/L, BUN in mg/dL, and select gender. All values must be valid positive numbers. This calculator is specifically designed for ages 1-25 years.

5. Frequently Asked Questions (FAQ)

Q1: Why use CKiD U25 instead of adult equations?
A: Pediatric equations account for growth, development, and body composition changes that affect kidney function differently than in adults.

Q2: What are normal eGFR values for children?
A: Normal pediatric eGFR values vary by age and body size, generally ranging from 90-140 mL/min/1.73m², with higher values in younger children.

Q3: When is cystatin C measurement preferred?
A: Cystatin C is particularly useful in children with muscle wasting, malnutrition, or conditions affecting muscle mass where creatinine may be misleading.

Q4: Are there age limitations for this equation?
A: This equation is validated for ages 1-25 years. For infants under 1 year or adults over 25, other equations should be used.

Q5: How does height affect the calculation?
A: Height is used to normalize GFR to body surface area (1.73m²), which is standard practice in pediatric nephrology for comparing kidney function across different body sizes.