Medscape Creatinine Clearance Calculator

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 in clinical practice for drug dosing adjustments and assessing renal function.

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:

\( CrCl \) — Creatinine clearance (mL/min)
\( Age \) — Age in years
\( Weight \) — Body weight in kilograms
\( SCr \) — Serum creatinine (mg/dL)
0.85 — Female gender multiplier

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

3. Importance of Creatinine Clearance Calculation

Details: Creatinine clearance is essential for determining appropriate drug dosages for medications that are renally excreted, assessing kidney function, and monitoring patients with renal impairment.

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 use Cockcroft-Gault instead of other equations?
A: Cockcroft-Gault is well-validated and commonly used for drug dosing adjustments, especially for medications with narrow therapeutic windows.

Q2: What are normal creatinine clearance values?
A: Normal values are approximately 95-105 mL/min for men and 85-95 mL/min for women, declining with age.

Q3: When should ideal body weight be used?
A: For obese patients, ideal body weight may be used instead of actual body weight to avoid overestimating renal function.

Q4: Are there limitations to this equation?
A: Less accurate in elderly patients, those with extreme body weights, muscle wasting conditions, or rapidly changing kidney function.

Q5: Can this be used for all drug dosing?
A: While widely used, some medications may require more precise GFR estimation methods or measured creatinine clearance for optimal dosing.