A positive (+) result of bilirubin in urine (bilirubinuria) is indicative of a liver problem or a bile obstruction.
Bilirubin has a strong yellow-orange color. When it becomes elevated in the bloodstream, the patient’s skin and eyes (sclera of the eye) reflect this intense yellow color, known as jaundice. When it becomes elevated in the urine it gives urine a dark or brown color called choluria. In addition, bilirubin in urine may cause a foamy urine when it is shaken.
Bilirubin is a by-product of red blood cell destruction at the end of their life cycle. The bilirubin, created from hemoglobin as part of this degradation process, is not water-soluble and it is called unconjugated or indirect bilirubin. This type of bilirubin travels through the bloodstream and it is later processed in the liver, where it becomes water-soluble and it is called conjugated or direct bilirubin.
The only type of bilirubin ever found in the urine is the conjugated (direct) bilirubin because it is the only one that can cross the glomerular filter in the kidneys. Normally, bilirubin is not present in the urine because it has been previously converted to urobilinogen in the intestine.
The presence of bilirubin in the urine sample may be an early indication of liver disease (cirrhosis, hepatitis) or bile obstruction (obstructive jaundice).
The bilirubin urine test is a screening procedure usually performed to detect liver disorders, such as hepatitis, before any other symptom may be present or on populations that were known to be exposed to hepatitis.
It may also be useful to screen blood donors, food handlers, and other possible carriers of the disease when it is imperative to avoid a possible transmission of hepatitis in subclinical cases (people that do not know that they are infected).
Besides, it is helpful to discern between genetic disorders with an elevated bilirubin in the blood but not in the urine. For example, Gilbert’s syndrome or Crigler-Najjar cause an increase of bilirubin in the blood but not in the urine. In contrast, Rotor syndrome or Dubin-Johnson syndrome cause an elevation of bilirubin in the blood and urine simultaneously.
This bilirubin urine test is usually performed at the same time of urobilinogen urine test because they are closely related and both provide a better information for the diagnosis.
This test is performed along with other urine tests. The patient must collect a sample of the urine in a specific container using a special kit. This sample will be sent to the lab for the analysis.
The urine must be fresh because oxidation affects the results, and exposure to strong lights also changes the chemical composition of the bilirubin.
Bilirubin in urine can be tested either with a dipstick or with a tablet that change of color in the presence of a high amount of bilirubin in the urine.
In laboratories, there are automated machines that perform the analysis, but it is also possible to buy strips that let you analyze a urine sample at home. They comprise up to 10 or more different reagents or chemical pads to perform different urine tests at the same time.
The bilirubin urine test must be negative to be considered within normality. For this matter, the level of bilirubin in urine should be below 0.2 mg/dl (equivalent to 0.34 µmol/l).
A positive result of bilirubin (bilirubin in urine +) may be due to:
Some drugs or substance may interfere with the bilirubin urine test: