1. What Is Measured Creatinine Clearance?

Measured creatinine clearance is a direct assessment of kidney function using timed urine collection and simultaneous plasma creatinine measurement. It provides an accurate estimate of glomerular filtration rate (GFR) by calculating the volume of plasma cleared of creatinine per minute.

2. How Does The Calculator Work?

The calculator uses the measured creatinine clearance formula:

Where:

• \( CrCl \) — Creatinine clearance (mL/min)
• \( U_{cr} \) — Urine creatinine concentration (mg/dL)
• \( V \) — Urine flow rate (mL/min)
• \( P_{cr} \) — Plasma creatinine concentration (mg/dL)

Explanation: This formula calculates the volume of plasma that would be completely cleared of creatinine per minute based on the amount excreted in urine.

3. Importance Of Measured CrCl

Details: Measured creatinine clearance is considered the gold standard for GFR estimation and is particularly useful when estimated equations may be inaccurate, such as in patients with extreme body size, muscle mass, or rapidly changing kidney function.

4. Using The Calculator

Tips: Enter urine creatinine in mg/dL, urine volume in mL/min, and plasma creatinine in mg/dL. All values must be positive. For accurate results, ensure proper 24-hour urine collection and simultaneous plasma sampling.

5. Frequently Asked Questions (FAQ)

Q1: Why use measured CrCl instead of estimated equations?
A: Measured CrCl provides direct assessment of kidney function and is more accurate in patients with unusual body composition, amputations, or when precise drug dosing is critical.

Q2: What is the proper urine collection method?
A: 24-hour urine collection is standard. Discard first morning void, then collect all urine for next 24 hours including first void of following morning.

Q3: How do I calculate urine flow rate (V)?
A: Divide total 24-hour urine volume (mL) by 1440 (minutes in 24 hours) to get mL/min.

Q4: What are normal CrCl values?
A: Normal range is approximately 90-120 mL/min for young adults, declining with age. Values below 60 mL/min suggest impaired kidney function.

Q5: What factors can affect CrCl accuracy?
A: Incomplete urine collection, improper timing, meat consumption before testing, exercise, and certain medications can affect results.