Definition This is a test of kidney function. It determines the amount of fluid filtered each minute by the kidneys.
Creatinine is produced in the muscles and filtered through the kidneys. Almost all the creatinine released from the muscles makes its way into the urine. Comparing the amount of creatinine in the blood with the amount of creatinine in the urine gives an indication of kidney function.
Who is a candidate for the test? Anyone suspected of having abnormal kidney functioning may require a creatinine clearance test.
How is the test performed? This test is performed on a 24-hour urine sample. The person should follow the specific instructions of the doctor on how to collect the urine sample. In general, this schedule is followed:
Day 1: The person urinates upon arising as usual. The person does not collect that sample. Then, the individual collects all urine produced for the next 24 hours in a special container.
Day 2: First thing in the morning, the person urinates into the container again. Then the individual covers it and refrigerates it. The sample is brought to the doctor.
The person will also be required to give a blood sample so the blood level of creatinine can be measured and compared with that found in the 24-hour collection of urine.
What is involved in preparation for the test? The person should request specific instructions from his or her doctor.
What do the test results mean? Normal values for creatinine clearance (glomerular filtration rates) are as follows:
males, 97 - 137 ml/min (millilitres per minute), or 1.6 - 2.3 ml/sec (millilitres per second)
females, 88 - 128 ml/min, or 1.5 - 2.1 ml/sec
Abnormally low glomerular filtration rates may indicate:
acute tubular necrosis, or kidney failure caused by damage to the kidney's tubules
Wilms' tumour, a cancer of the kidneys generally seen in infants and young children
Author: Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 17/11/2004 Contributors Potential conflict of interest information for reviewers available on request
