Creatinine Clearance

This is a test of kidney function. It measures the amountof fluid filtered each minute by the kidneys.

Creatinine is made in the muscles and filtered throughthe kidneys. Almost all the creatinine released from the muscles makesits way into the urine as a waste product. Comparing the amount ofcreatinine in the blood with the amount of creatinine in the urine givesan idea of how well the kidneys are functioning.

Who is a candidate for the test?

Anyone whose has kidneys that may not be functioning wellmay need a creatinine clearance test.

How is the test performed?

This test is done with a urine sample gathered over a 24-hour period. The personshould follow the specific instructions of the doctor on how to collect theurine sample. In general, this schedule is followed:

Day 1: The person urinates upon arising without collecting that sample.After that, he or she collects all of his or her urinefor the next 24 hours in a special container.

Day 2: First thing in the morning, the person urinates into thecontainer again. Then the individual covers it and refrigerates it. Thesample is brought to the doctor, who will send it to the lab for analysis.

The person will also have a blood sample doneso the blood level of creatinine can be measured and compared withthat found in the 24-hour urine sample.

What is involved in preparation for the test?

The person should request exact instructions from hisor her doctor.

What do the test results mean?

The healthy range of glomerular filtration rates forcreatinine clearance is as follows:

males, 97 to 137 milliliters/minute (mL/min)

females, 88 to 128 mL/min

Abnormally low glomerular filtration rates may suggest:

acute tubular necrosis,which is kidney failure caused by damage to the kidney’s tubules

heart failure

dehydration, which means the body lacks fluids

glomerulonephritis,which is an inflammation of the parts of the kidney that filter the blood

not having enough blood flow to the kidneys

shock,which is a life-threatening condition in which blood pressure falls too low tosupport life

obstructive uropathy,a kidney disease caused by blockage of the kidney’s drainage tubes

acute nephrotic syndrome, where the kidneys stop being able toperform their filtering role

acute kidney failure

other types of kidney disease

Wilms tumor,a cancer of the kidneys generally seen in infants and young children