Measured Creatinine Clearance Calculator

Creatinine Clearance Formula:

\[ CrCl = \frac{(U_{cr} \times V)}{P_{cr}} \]

Urine Creatinine (U_cr):

mg/dL

Urine Volume per Minute (V):

mL/min

Plasma Creatinine (P_cr):

mg/dL

Creatinine Clearance (CrCl):

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1. What is Measured Creatinine Clearance?

Measured Creatinine Clearance is a direct measurement of the kidney's ability to filter creatinine from the blood. Unlike estimated GFR, it requires collection of both blood and timed urine samples to provide an accurate assessment of renal function.

2. How Does the Calculator Work?

The calculator uses the creatinine clearance formula:

\[ CrCl = \frac{(U_{cr} \times V)}{P_{cr}} \]

Where:

\( U_{cr} \) — Urine creatinine concentration (mg/dL)
\( V \) — Urine volume per minute (mL/min)
\( P_{cr} \) — Plasma creatinine concentration (mg/dL)

Explanation: This formula calculates the volume of plasma cleared of creatinine per minute, providing a direct measurement of glomerular filtration rate.

3. Importance of Creatinine Clearance

Details: Measured creatinine clearance is considered the gold standard for assessing kidney function and is particularly important for drug dosing in patients with unstable renal function or those requiring precise medication adjustments.

4. Using the Calculator

Tips: Enter urine creatinine in mg/dL, urine volume per minute in mL/min, and plasma creatinine in mg/dL. All values must be positive numbers. Ensure proper 24-hour urine collection for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: Why measure creatinine clearance instead of using eGFR?
A: Measured CrCl provides actual kidney function measurement, while eGFR is an estimate. CrCl is more accurate in patients with muscle wasting, obesity, or rapidly changing renal function.

Q2: How is urine volume per minute calculated?
A: Collect 24-hour urine, measure total volume in mL, then divide by 1440 (minutes in 24 hours) to get mL/min.

Q3: What are normal creatinine clearance values?
A: Normal range is approximately 90-120 mL/min for young adults, decreasing with age. Values below 60 mL/min indicate impaired kidney function.

Q4: What factors affect creatinine clearance accuracy?
A: Incomplete urine collection, meat consumption before testing, vigorous exercise, and certain medications can affect results.

Q5: When is measured CrCl preferred over eGFR?
A: For precise drug dosing (especially nephrotoxic drugs), in critically ill patients, and when eGFR may be unreliable due to extreme body composition.