GFR Calculator Including 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 approximation of glomerular filtration rate (GFR).

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 in mg/dL
0.85 — Female multiplier (accounts for lower muscle mass)
72 — Constant factor in the equation

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 crucial for appropriate drug dosing in patients with renal impairment, assessing kidney function, and monitoring patients at risk for kidney disease.

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).

5. Frequently Asked Questions (FAQ)

Q1: Why include weight in this calculation?
A: Weight is included because creatinine production is proportional to muscle mass, which correlates with body weight.

Q2: 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.

Q3: When is this equation most useful?
A: Particularly useful for drug dosing adjustments in elderly patients and those with chronic kidney disease.

Q4: Are there limitations to this equation?
A: Less accurate in extremes of body weight (obesity, cachexia), amputees, and patients with rapidly changing kidney function.

Q5: How does this compare to other GFR equations?
A: Cockcroft-Gault includes weight and is commonly used for drug dosing, while CKD-EPI and MDRD provide more accurate GFR estimation for diagnosis.