Creatinine Clearance calculation, normal and abnormal values, significance

This is a discussion of Creatinine Clearance test , which is one of the Kidney function tests .
We are going to discuss its normal and abnormal values, methods and equations of calculation and  its significance .
• It is a method to measure GFR approximately.
• It is the volume of plasma cleared from creatinine / min. = U x V / P

U = urine creatinine mg/dl.
V = voIume of urine / min. = Urine volume in 24hrs / 1440
P = plasma creatinine mg/dl.

Normal Value

90-140 ml/min for males, 80-125 ml/min for females)
• Serum creatinine starts elevation when creatinine clearance <  25%-30%.
• The glomerular filtration rate (GFR) varies with age and sex but is approximately 120-130 ml/min/1.73 m2 surface area.
 It can be measured by renal scan using Diethylene triamine penta-acetic acid labeled with technetium (99mTc-DTPA), it is more accurate than creatinine clearance.
- GFR 35-50% of normal is sufficient to maintain the patient symptom-free, at GFR 20-35% azotemia occurs with initial manifestations of renal insutticiency, at GFR < 20-25% the patient develops overt rena! failure.

Calculation of creatinine clearance (Cockcroft & Gault equation) 

creatinine-clearance-equation

The calculated clearance should be reduced by 15% for women.

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