Creatinine Clearance Calculator Medscape

Cockcroft-Gault Equation:

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

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 is a widely used formula for estimating creatinine clearance (CrCl), which serves as a surrogate for glomerular filtration rate (GFR). It's particularly useful for medication dosing adjustments in patients with renal impairment.

2. How Does the Calculator Work?

The calculator uses the Cockcroft-Gault equation:

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

Where:

\( Age \) — Age in years
\( Weight \) — Body weight in kilograms
\( SCr \) — Serum creatinine in mg/dL
\( 0.85 \) — Adjustment factor for female gender

Explanation: The equation estimates creatinine clearance based on age, weight, serum creatinine, and gender, providing a practical tool for renal function assessment.

3. Importance of CrCl Calculation

Details: Creatinine clearance estimation is essential for drug dosing adjustments, particularly for medications with narrow therapeutic windows that are renally excreted. It helps prevent toxicity in patients with impaired kidney function.

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 widely validated for drug dosing adjustments and is referenced in many medication guidelines and prescribing information.

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

Q3: When should this calculation be used?
A: Primarily for medication dosing adjustments in patients with known or suspected renal impairment, especially for drugs with renal excretion.

Q4: Are there limitations to this equation?
A: Less accurate in elderly, obese, malnourished patients, and those with unstable renal function. May overestimate GFR in patients with reduced muscle mass.

Q5: How does this differ from eGFR?
A: CrCl estimates creatinine clearance while eGFR estimates glomerular filtration rate. CrCl is often preferred for drug dosing, while eGFR is used for CKD staging.