Creatinine Clearance

Category:

Creatinine Clearance

Description

Creatinine clearance test is a calculation of the amount of blood that is being filtered by the kidneys in 24 hours. Since the amount of creatinine produced depends on muscle mass, some calculations also use a correction factor in order to take into account the patient’s  height and weight.

This test helps evaluating kidney dysfunction.   It is prescribed when doctor thinks that there may be a problem affecting the function of the kidneys or another disease, such as congestive heart failure.

Purpose of the test

This test measures the amount of creatinine in the blood and urine to help evaluate the kidneys’ filtering ability.

Creatinine is a waste product derived from creatine, a nitrogen-based organic compound used by muscles to store energy. The amount of creatinine produced in the body is dependent on muscle mass and is constant for an individual. It is removed from the body by filtering units called glomeruli as blood passes through the kidneys. The amount of creatinine taken from the blood depends on the filtering ability of the glomeruli and the rate at which blood is carried to the kidneys. If the glomeruli are damaged or diseased, or if blood circulation is slowed, then less creatinine will be removed from the blood and released into the urine.

Reference range values

Creatinine Clearance (Corrected) mL/min/1.73m2
(SI: mL/s/m^2= 0.00963 x mL/min/1.73m^2)

Male 13Y-150Y      90 – 130
Female 13Y-150Y  80 – 125

Creatinine Clearance (Uncorrected) mL/min
(SI: mL/s = 0.0166 x mL/min)
0Y-1Y      35 – 65
1Y-12Y    60 – 90
>=13Y     90 – 125

In order to correct creatinine clearance for body surface area:
Creatinine clearance in mL/min x 1.73 / patient body surface area.

Body surface area:
BSA = (W0.425 x H0.725) / 139.315
W=weight (kg)
H=height (cm)

Abnormal findings

High creatinine in blood levels means decreased kidneys’ ability to clear creatinine and other wastes out of the blood.   Then creatinine clearance will be decreased in the urine.

Low creatinine clearance rate can also occur when there is decreased blood flow to the kidneys: as may occur with congestive heart failure, obstruction within the kidney, or acute or chronic kidney failure.
Increased creatinine clearance rates may occasionally be seen during pregnancy, exercise, and with diets high in meat.
Patients with only one functional kidney will usually have normal creatinine clearance rates as the functional kidney will increase its rate of filtration.