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 for drug dosing adjustments in patients with renal impairment and for assessing kidney 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:

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

Explanation: The equation estimates creatinine clearance based on demographic and laboratory parameters, with adjustment for gender differences in muscle mass.

3. Importance of Creatinine Clearance Calculation

Details: Creatinine clearance is crucial for drug dosing adjustments, particularly for medications with narrow therapeutic windows that are renally eliminated. 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: What is the difference between CrCl and eGFR?
A: CrCl estimates creatinine clearance using Cockcroft-Gault, while eGFR estimates glomerular filtration rate using equations like CKD-EPI. They serve different clinical purposes.

Q2: When is Cockcroft-Gault preferred over other equations?
A: Cockcroft-Gault is often preferred for drug dosing adjustments, particularly in older medications and clinical trials where it was the standard.

Q3: 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.

Q4: Are there limitations to the Cockcroft-Gault equation?
A: Less accurate in extremes of age, obesity, malnutrition, amputees, and patients with rapidly changing kidney function or unstable creatinine.

Q5: Should ideal body weight be used?
A: For obese patients, some guidelines recommend using ideal body weight rather than actual weight to avoid overestimating CrCl.