Estimated Creatinine Clearance Calculated Using Actual Body Weight

Cockcroft-Gault Equation (Actual Body Weight):

\[ CrCl = \frac{(140 - Age) \times Actual\ body\ weight \times (0.85\ if\ female)}{72 \times SCr} \]

Age:

years

Actual Body 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 with actual body weight:

\[ CrCl = \frac{(140 - Age) \times Actual\ body\ weight \times (0.85\ if\ female)}{72 \times SCr} \]

Where:

\( Age \) — Age in years
\( Actual\ body\ weight \) — Body weight in kilograms
\( SCr \) — Serum creatinine in mg/dL
\( 0.85 \) — Female multiplier (accounts for lower muscle mass)
\( 72 \) — Constant factor

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 Creatinine Clearance Calculation

Details: Accurate creatinine clearance estimation is crucial for drug dosing adjustments, assessing renal function, and identifying patients at risk for drug toxicity due to impaired kidney function.

4. Using the Calculator

Tips: Enter age in years, actual body 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: When should actual body weight vs ideal body weight be used?
A: Actual body weight is typically used unless the patient is obese (BMI > 30), in which case adjusted body weight may be more appropriate.

Q2: What are normal CrCl values?
A: Normal CrCl is approximately 90-120 mL/min for young adults, decreasing with age. Values below 60 mL/min indicate renal impairment.

Q3: How does this differ from eGFR?
A: CrCl estimates creatinine clearance while eGFR estimates glomerular filtration rate. CrCl is often higher than eGFR and is preferred for drug dosing.

Q4: Are there limitations to this equation?
A: Less accurate in elderly, malnourished patients, amputees, and those with unstable renal function or extreme body weights.

Q5: Why is the female multiplier 0.85?
A: This accounts for typically lower muscle mass in females compared to males of the same weight and age.