eGFR Calculator with Weight

Cockcroft-Gault Equation:

\[ CrCl = \frac{(140 - Age) \times Weight \times (0.85 \text{ if female})}{72 \times Scr} \]

Age:

years

Weight:

Serum Creatinine (Scr):

mg/dL

Gender:

Creatinine Clearance (CrCl):

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1. What is the Cockcroft-Gault Equation?

The Cockcroft-Gault equation estimates creatinine clearance (CrCl) from serum creatinine, age, weight, and gender. It is widely used for drug dosing adjustments in patients with renal impairment and provides an estimate of glomerular filtration rate.

2. How Does the Calculator Work?

The calculator uses the Cockcroft-Gault equation:

\[ CrCl = \frac{(140 - Age) \times Weight \times (0.85 \text{ if female})}{72 \times Scr} \]

Where:

\( Age \) — Age in years
\( Weight \) — Body weight in kilograms
\( Scr \) — Serum creatinine (mg/dL)
0.85 — Female multiplier (accounts for lower muscle mass)

Explanation: The equation estimates creatinine clearance based on the principle that creatinine production is proportional to muscle mass, which decreases with age and is generally lower in females.

3. Importance of CrCl Calculation

Details: Creatinine clearance estimation is essential for adjusting medication dosages in patients with renal impairment, particularly for drugs that are primarily eliminated by the kidneys. It helps prevent drug toxicity and ensures therapeutic efficacy.

4. Using the Calculator

Tips: Enter age in years, weight in kilograms, serum creatinine in mg/dL, and select gender. All values must be valid (age between 1-120, weight > 0, creatinine > 0). Use actual body weight for calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between CrCl and eGFR?
A: CrCl (Cockcroft-Gault) is often used for drug dosing, while eGFR (CKD-EPI/MDRD) is used for diagnosing and staging chronic kidney disease. They may give different values.

Q2: Should I use ideal body weight or actual body weight?
A: For most clinical purposes, use actual body weight. For obese patients, some guidelines suggest using adjusted body weight or ideal body weight.

Q3: What are normal CrCl values?
A: Normal CrCl is approximately 95-125 mL/min for young adults, decreasing with age. Values below 60 mL/min indicate renal impairment.

Q4: Are there limitations to this equation?
A: Less accurate in elderly, malnourished, obese patients, and those with unstable renal function. Not validated in children or pregnant women.

Q5: When is this equation most useful?
A: Primarily for drug dosing adjustments, especially for medications with narrow therapeutic windows that require renal dose adjustment.