Creatinine Clearance Calculation UK

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
\( 0.85 \) — 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: Creatinine clearance is crucial for drug dosing adjustments, particularly for medications that are renally eliminated. It helps prevent toxicity in patients with impaired kidney function and ensures therapeutic efficacy.

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 while eGFR estimates glomerular filtration rate. CrCl is often used for drug dosing, while eGFR is used for CKD staging.

Q2: What are normal CrCl values?
A: Normal CrCl is approximately 95-125 mL/min for young adults, decreasing with age. Values below 60 mL/min indicate renal impairment.

Q3: When should the Cockcroft-Gault equation not be used?
A: It may be less accurate in extremes of age, obesity, malnutrition, amputees, and patients with rapidly changing kidney function.

Q4: Why is weight included in the equation?
A: Weight serves as a surrogate for muscle mass, which correlates with creatinine production.

Q5: Can this calculator be used for pediatric patients?
A: No, the Cockcroft-Gault equation is validated for adults only. Different equations should be used for pediatric patients.