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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.
This test is performed on a 24-hour urine sample. The person should
follow the specific instructions of the healthcare provider 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 healthcare provider.
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.
Normal values for creatinine clearance (glomerular filtration rates)
are as follows:
males, 97 to 137 milliliters/minute (ml/min)
females, 88 to 128 milliliters/minute
Abnormally low glomerular filtration rates may indicate:
- acute tubular necrosis, or kidney failure caused by damage to
the kidney's tubules
- heart failure
- dehydration, or lack of fluids
- glomerulonephritis, or inflammation of the parts of the kidney
that filter the blood
- inadequate blood flow to the kidneys
- shock, a life-threatening condition in which blood pressure falls
too low to support life
- obstructive uropathy, a kidney disease caused by blockage of the
kidney's drainage tubes
- acute nephrotic syndrome, the sudden inability of kidneys to perform
their filtering role
- acute kidney failure
- kidney disease
- Wilms' tumor, a cancer of the kidneys generally seen in infants
and young children
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