GFR Calculator Cockcroft Formula

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), which serves as a surrogate for glomerular filtration rate (GFR). It was developed in 1976 and remains one of the most commonly used equations for drug dosing adjustments in patients with renal impairment.

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:

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

Explanation: The formula estimates creatinine clearance based on age, weight, serum creatinine, and gender. It assumes a linear relationship between creatinine production and muscle mass.

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 chronic 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, creatinine > 0 mg/dL).

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 men and 85-115 mL/min for women. Values decrease with age.

Q3: When should ideal body weight be used instead of actual weight?
A: For obese patients (BMI > 30), ideal body weight is often recommended to avoid overestimation of renal function.

Q4: What are the limitations of the Cockcroft-Gault formula?
A: Less accurate in elderly, malnourished, obese patients, and those with unstable renal function. It may overestimate CrCl in patients with reduced muscle mass.

Q5: Is this formula suitable for all patient populations?
A: While widely used, it may not be optimal for elderly patients, those with extremes of body weight, or patients with rapidly changing renal function.