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Creatinine Clearance test

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What is a Creatinine Clearance test?

Creatinine is produced normally in the body as a by-product of normal muscle breakdown. It is then removed from the bloodstream by the kidneys. This is an ongoing process within the body and any variation indicates some kind of problem. The Creatinine Clearance test measures the amount of creatinine excreted in the urine over 24 hours. A comparison between creatinine levels in the blood with that of urine is made to arrive at the results.

Why is it conducted?

  • This test is primarily conducted to check whether the kidneys are working properly.
  • It also forms the basis of finding out the eGFR or the estimated glomerular filtration rate. Glomeruli are the filters within the kidney.
  • In addition to this, it indicates whether there is proper flow of blood to the kidneys.
  • It also helps to assess dehydration level in the body.

Who should go for it?

  • Persons who are taking medicines that can affect kidney function should take this test to test for possible damage.
  • People who have chronic diseases that can damage kidney function like diabetes or high blood pressure and other diseases like congestive heart failure, suspected obstruction and so on.
  • Persons who have pain where the kidneys are located or midback just below the ribs.
  • People who show signs of kidney disease like puffiness around the eyes and lower limbs, reduced levels of urine, presence of blood or foamy urine.
  • Persons who have been diagnosed with kidney disease are advised this test for monitoring the progress of the disease. The creatinine clearance test is an accurate measure of kidney function and is therefore advised for grading of chronic kidney disease.

Procedure

This test involves both a blood test and urine test. The blood is drawn by a technician at the testing laboratory. The urine is collected by the patient at home and the procedure for collection should be followed carefully for there to be accurate results. A container containing some preservative is provided for collection. One should begin collection in the morning after the first urine of the day. Note the time of emptying the bladder but do not collect this urine. From then onwards collect all the urine that you pass for the next 24 hours.

Precautions

Remember to keep the sample refrigerated.

  • Do not touch the inside of the container.
  • Do not indulge in any vigorous exercise for 48 hours before and during the test as this can stimulate excess production of creatinine in the body.
  • Empty your bladder just before the 24 hours are complete and add this urine in the collected sample.
  • Make sure that no other matter like hair, stool, menstrual blood contaminates the sample.

Interpretation of results

The results of the creatinine clearance test are expressed as number of units excreted in a minute or a second. The normal ranges for men are 107-139 milliliters per minute and for women 87-107 mL/min. These are for people below the age of 40. It is quite normal for the rate of creatinine clearance to be lower as one ages. Therefore the results are always read in tandem with the age of the person being tested. A low creatinine clearance result indicates less than normal functioning of the kidneys. It is expected that blood creatinine levels will be high along with low creatinine clearance results.

Certain antibiotics like aminoglycosides or cephalosporins and other medicines, namely cisplatin for cancer and cimetidine for stomach acid can also affect results. Besides this, creatinine clearance levels are high during pregnancy.

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Written by: Nandita tripati

Date last updated: January 10, 2015