Calculating Creatinine Clearance

Cockcroft-Gault Formula:

\[ CrCl = \frac{(140 - age) \times weight \times 0.85 \text{ (if female)}}{72 \times SCr} \]

Age:

years

Weight:

Serum Creatinine (SCr):

mg/dL

Gender:

Creatinine Clearance (CrCl):

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1. What is the Cockcroft-Gault Formula?

The Cockcroft-Gault formula is a widely used method for estimating creatinine clearance (CrCl) from serum creatinine, age, weight, and gender. It helps assess kidney function and guide medication dosing, particularly for drugs that are renally eliminated.

2. How Does the Calculator Work?

The calculator uses the Cockcroft-Gault formula:

\[ CrCl = \frac{(140 - age) \times weight \times 0.85 \text{ (if female)}}{72 \times SCr} \]

Where:

\( CrCl \) — Creatinine clearance (mL/min)
\( age \) — Age in years
\( weight \) — Body weight in kilograms
\( SCr \) — Serum creatinine (mg/dL)
\( 0.85 \) — Adjustment factor for female gender

Explanation: The formula estimates the rate at which creatinine is cleared from the blood by the kidneys, providing an approximation of glomerular filtration rate.

3. Importance of CrCl Calculation

Details: Creatinine clearance estimation is essential for drug dosing adjustments in patients with renal impairment, assessing kidney function, and monitoring the progression of 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 1-120 years, weight > 0 kg, SCr > 0 mg/dL).

5. Frequently Asked Questions (FAQ)

Q1: Why use Cockcroft-Gault formula?
A: It's a well-validated method for estimating creatinine clearance and is commonly used for drug dosing adjustments in clinical practice.

Q2: What are normal CrCl values?
A: Normal CrCl is approximately 95-125 mL/min for men and 85-115 mL/min for women, decreasing with age.

Q3: When should this calculation be used?
A: Primarily for drug dosing adjustments, especially for medications with narrow therapeutic windows that are renally eliminated.

Q4: Are there limitations to this formula?
A: Less accurate in elderly, obese, or severely ill patients, and in those with rapidly changing kidney function or extremely low muscle mass.

Q5: How does this differ from eGFR?
A: CrCl estimates actual creatinine clearance, while eGFR estimates glomerular filtration rate standardized to body surface area. CrCl is often preferred for drug dosing.