DaVita Kidney GFR Calculator

GFR Calculation:

\[ GFR = \text{CKD-EPI or MDRD formula} \]

Serum Creatinine (Scr):

mg/dL

Age:

years

Gender:

Race:

Formula:

Estimated GFR:

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1. What is GFR?

Glomerular filtration rate (GFR) is the best overall index of kidney function. It represents the flow rate of filtered fluid through the kidney and is expressed in mL/min/1.73m².

2. CKD-EPI vs MDRD Formulas

CKD-EPI Equation:

\[ eGFR = 141 \times \min(Scr/\kappa, 1)^\alpha \times \max(Scr/\kappa, 1)^{-1.209} \times 0.993^{age} \times (1.018 \text{ if female}) \times (1.159 \text{ if black}) \]

MDRD Equation:

\[ eGFR = 175 \times (Scr)^{-1.154} \times (age)^{-0.203} \times (0.742 \text{ if female}) \times (1.212 \text{ if black}) \]

Comparison: CKD-EPI is generally more accurate, especially at higher GFR levels (>60), while MDRD may be more familiar to some clinicians.

3. Importance of GFR Calculation

Details: GFR estimation is essential for diagnosing and staging chronic kidney disease, monitoring disease progression, and adjusting medication dosages.

4. Using the Calculator

Tips: Select your preferred formula (CKD-EPI or MDRD), enter serum creatinine in mg/dL, age in years, and select gender and race. All values must be valid.

5. Frequently Asked Questions (FAQ)

Q1: Which formula should I use?
A: CKD-EPI is now recommended for routine clinical use as it's more accurate, but MDRD may be needed for comparison with older studies.

Q2: What are normal GFR values?
A: Normal GFR varies by age but is generally ≥90 mL/min/1.73m² in young adults, decreasing with normal aging.

Q3: Why does race affect GFR calculation?
A: Studies show that Black individuals have higher muscle mass on average, affecting creatinine production and thus requiring adjustment.

Q4: When should I use measured GFR instead?
A: Consider measured GFR (e.g., with iohexol or iothalamate) in patients with extremes of muscle mass, amputees, or when very precise measurement is needed.

Q5: How often should GFR be monitored?
A: Frequency depends on clinical context - annually for screening, more often (e.g., every 3-6 months) for known CKD or high-risk patients.