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Bilirubin - urine
Alternative namesConjugated bilirubin-urine; Direct bilirubin-urine
This is a urine test that measures the amount of bilirubin .
Bilirubin metabolism begins with the breakdown of red blood cells (RBCs) by phagocytic cells (cells that consume and digest other cells). Hemoglobin is broken down to heme and globin. Heme is converted to bilirubin, which is then carried by albumin in the blood to the liver.
In the liver, most of the bilirubin is conjugated with glucuronic acid before it is excreted in the bile . Conjugated bilirubin is called direct bilirubin (DB), and unconjugated bilirubin is called indirect bilirubin (IB). Total bilirubin = DB + IB. Conjugated bilirubin is excreted into the bile by the liver and stored in the gall bladder or transferred directly to the small intestines.
How the test is performedA 24-hour urine sample is needed. The health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test.
For an infant:
The infant should be checked frequently and the bag changed after the infant has urinated into the bag. For active infants, this procedure may take a couple of attempts, as the bag is easily displaced. The urine is drained into the container for transport to the laboratory.
How to prepare for the testNo special preparation is necessary for this test, but if the collection is being taken from an infant, a couple of extra collection bags may be necessary.
How the test will feelThe test involves only normal urination, and there is no discomfort.
Why the test is performedThis test may be performed when liver or gallbladder problems are suspected.
Normal ValuesBilirubin is not normally found in the urine.
What abnormal results meanIf the bile ducts are obstructed, direct bilirubin will build up to a high enough level that some of it will escape from the liver into the blood. If the levels are high enough, some of it will also appear in the urine. Only direct bilirubin appears in the urine. Increased direct bilirubin usually means that the biliary (liver secretion) ducts are obstructed.
Increased urinary bilirubin may indicate:
What the risks areThere are no risks.
Special considerationsBilirubin can decompose in the presence of light.
Drugs than can falsely elevate the test result include allopurinol, some antibiotics, barbiturates, chlorpromazine, diuretics, ethoxazene, oral contraceptives, phenazopyridine, steroids, and sulfonamides.
Drugs that can cause false negative results include indomethacin and ascorbic acid .
Update Date: 8/18/2003David Webner, M.D., Sports Medicine Fellow, Crozer-Keystone Family Practice Program, Springfield, PA. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT