Global RPH Clearance Calculator (Creatinine)

Creatinine Clearance Formula:

\[ CrCl = \frac{(140 - age) \times weight \times (0.85\ if\ female)}{72 \times Scr} \]

Age:

years

Weight:

Serum Creatinine (Scr):

mg/dL

Gender:

Creatinine Clearance (CrCl):

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1. What is Creatinine Clearance?

Definition: Creatinine clearance (CrCl) is a measure of kidney function that estimates the glomerular filtration rate (GFR) - the volume of blood cleared of creatinine per minute.

Purpose: It helps healthcare providers assess kidney function, adjust medication dosages, and monitor renal impairment.

2. How Does the Calculator Work?

The calculator uses the Cockcroft-Gault formula:

\[ CrCl = \frac{(140 - age) \times weight \times (0.85\ if\ female)}{72 \times Scr} \]

Where:

\( CrCl \) — Creatinine clearance (mL/min)
\( age \) — Patient's age in years
\( weight \) — Patient's weight in kilograms
\( Scr \) — Serum creatinine level (mg/dL)
\( 0.85 \) — Adjustment factor for female patients

Explanation: The formula estimates how efficiently the kidneys are clearing creatinine from the blood based on age, weight, gender, and creatinine level.

3. Importance of Creatinine Clearance

Details: CrCl is crucial for determining appropriate drug dosages, especially for medications that are primarily excreted by the kidneys. It helps prevent drug toxicity in patients with impaired renal function.

4. Using the Calculator

Tips: Enter the patient's age (18-120 years), weight in kg, serum creatinine level in mg/dL, and select gender. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is there a different calculation for females?
A: Women typically have less muscle mass than men, and creatinine production is related to muscle mass. The 0.85 factor adjusts for this difference.

Q2: What is a normal CrCl range?
A: Normal range is approximately 90-120 mL/min for young adults. Values below 60 mL/min indicate some degree of renal impairment.

Q3: When should this calculation not be used?
A: The formula may be less accurate in elderly, very obese or underweight patients, amputees, or those with rapidly changing creatinine levels.

Q4: How does age affect CrCl?
A: Kidney function naturally declines with age, which is reflected in the (140 - age) component of the formula.

Q5: What if my patient's weight changes significantly?
A: Recalculate with the current weight, as CrCl is weight-dependent. For obese patients, some clinicians use ideal body weight instead.