eGFR Calculator MDRD Nephron

MDRD Nephron Equation:

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

Serum Creatinine (Scr):

mg/dL

Age:

years

Gender:

Race:

Estimated GFR (eGFR):

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1. What is the MDRD Nephron Equation?

The MDRD (Modification of Diet in Renal Disease) Nephron equation estimates glomerular filtration rate (GFR) from serum creatinine, age, sex, and race. It was developed to provide a more accurate assessment of kidney function in patients with chronic kidney disease.

2. How Does the Calculator Work?

The calculator uses the MDRD Nephron equation:

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

Where:

\( Scr \) — Serum creatinine (mg/dL)
\( Age \) — Age in years
0.742 — Female multiplier
1.212 — Black race multiplier

Explanation: The equation uses a power function relationship between creatinine and GFR, with demographic adjustments for gender and race.

3. Importance of eGFR Calculation

Details: Accurate GFR estimation is essential for diagnosing chronic kidney disease, monitoring disease progression, and adjusting medication dosages based on renal function.

4. Using the Calculator

Tips: Enter serum creatinine in mg/dL, age in years, select gender and race. All values must be valid (creatinine > 0, age between 1-120).

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between MDRD and CKD-EPI equations?
A: MDRD is more accurate in patients with established CKD, while CKD-EPI performs better at higher GFR levels and is less likely to misclassify individuals with normal or mildly reduced kidney function.

Q2: What are the limitations of the MDRD equation?
A: Less accurate in elderly patients, extremes of body size, pregnant women, and populations with different muscle mass or dietary patterns.

Q3: When was the MDRD equation developed?
A: The MDRD equation was developed in 1999 based on data from the Modification of Diet in Renal Disease study.

Q4: Is MDRD suitable for all patient populations?
A: While widely used, it may require validation or adjustment for specific ethnic groups not well represented in the original study population.

Q5: How often should eGFR be monitored?
A: Frequency depends on clinical context - from annually in stable patients to weekly in acute kidney injury or when adjusting nephrotoxic medications.