Creatinine clearance

Creatinine tests — A measurement of the serum creatinine level is often used to evaluate kidney function. Urine creatinine levels can be used as a screening test to evaluate kidney function, or can be part of the creatinine clearance test.

Definition

The creatinine clearance test compares the level of creatinine in urine with the creatinine level in the blood. (Creatinine is a breakdown product of creatine, which is an important part of muscle.) The test helps provide information on kidney function.

How the test is performed

This test requires both a blood and urine sample. You will collect your urine for 24 hours, and then have blood taken.

For information on giving a blood sample, see: venipuncture.
For information on how to collect the urine sample, see: 24-hour urine collection.

The samples are sent to a laboratory. The laboratory specialist measures the level of creatinine in both the urine and blood samples, and looks at how much urine you collected in 24 hours.

The clearance rate is then calculated. The calculation is adjusted for your specific body size.

The creatinine clearance appears to decrease with age (each decade corresponds to a decrease of about 6.5 ml/min./1.73 m2).

How to prepare for the test

If the collection is being taken from an infant, a couple of extra collection bags may be necessary.

How the test will feel

The urine test involves only normal urination and there is no discomfort. When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

The creatinine clearance test is used to estimate the glomerular filtration rate (GFR).

However, because a small amount of creatinine is released by the filtering tubes in the kidneys, creatinine clearance is not exactly thto the same as the GFR. In fact, creatinine clearance usually overestimates the GFR. This is particularly true in patients with advanced kidney failure.

Normal Values

Clearance is often measured as milliliters/minute (ml/min). Normal values are:

Male: 97 to 137 ml/min.
Female: 88 to 128 ml/min.

Note: Normal values ranges may vary slightly among different laboratories.

What abnormal results mean

Abnormal results (lower-than-normal creatinine clearance) may indicate:

Acute tubular necrosis
Bladder outlet obstruction
Congestive heart failure
Dehydration
Glomerulonephritis
Renal ischemia (blood deficiency
Renal outflow obstruction (usually must affect both kidneys to reduce the creatinine clearance)
Shock
Acute renal failure
Chronic renal failure
End-stage renal disease

What the risks are

The risks of the test are minimal and are related to the blood draw process. Rarely, the following will occur:

Excessive bleeding at blood draw site
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Multiple punctures to locate veins

Special considerations

Factors that may interfere with the accuracy of the test are as follows:

Incomplete urine collection
Pregnancy
Vigorous exercise

Drugs that can interfere with creatinine clearance measurements include: cimetidine, trimethoprim, and drugs that can damage the kidneys, such as cephalosporins.

The creatinine clearance test should only be done for patients who are medically stable. Such patients may have a rapidly changing creatinine clearance, and therefore any result may be inaccurate.

References

Bazari H. Approach to the patient with renal disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 115.

Disease

Acute nephritic syndrome

Acute nephritic syndrome is a group of disorders that cause swelling or inflammation of the internal kidney structures (specifically, the glomeruli). Nephritic syndrome is a type of .
Disease

Acute kidney failure

Acute (sudden) kidney failure is the sudden loss of the ability of the kidneys to remove waste and concentrate urine without losing .
Test

Urine 24-hour volume

The urine 24-hour volume test measures the amount of urine produced in a day.
Disease

End-stage kidney disease

End-stage kidney disease is the complete, or almost complete failure of the kidneys to function. The main function of the kidneys is to remove wastes and excess water from the body.
Disease

Wilms tumor

Wilms tumor is a type of kidney cancer that occurs in children.
Disease

Acute bilateral obstructive uropathy

Acute bilateral obstructive uropathy is a sudden blockage of the flow of urine from both kidneys. The kidneys continue to produce urine in the normal manner, but because urine does not drain properly, the kidneys start to swell. See also:
Injury

Shock

Shock is a life-threatening condition that occurs when the body is not getting enough blood flow. This can damage multiple organs. Shock requires immediate medical treatment and can get worse very rapidly.
Test

Creatinine - blood

Creatinine is a breakdown product of creatine, which is an important part of muscle. This article discusses the laboratory test to measure the amount of creatinine in the blood. Creatinine can also be measured with a urine test. See:
Disease

Heart failure

Heart failure, also called congestive heart failure, is a condition in which the heart can no longer pump enough blood to the rest of the body.
Disease

Acute tubular necrosis

Acute tubular necrosis is a kidney disorder involving damage to the tubule cells of the kidneys, resulting in .
Disease

Rapidly progressive glomerulonephritis

Rapidly progressive glomerulonephritis is a form of that causes damage to the small structures (glomeruli) inside the kidneys that help filter waste and fluids from blood to form urine. The disease leads to a rapid loss of kidney function.

Review date:: August 10, 2009
Reviewed by:: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2008 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.