Bilirubin is not present in the urine of normal, healthy individuals. Bilirubin is a waste product that is produced by the liver from the hemoglobin of RBCs that are removed from circulation. It becomes a component of bile, a fluid that is secreted into the intestines to aid in food digestion.
In certain liver diseases, such as biliary obstruction or hepatitis, bilirubin leaks back into the blood stream and is excreted in urine. The presence of bilirubin in urine is an early indicator of liver disease and can occur before clinical symptoms such as jaundice develop.
Urobilinogen is normally present in urine in low concentrations. It is formed in the intestine from bilirubin, and a portion of it is absorbed back into the bloodstream. Positive test results help detect liver diseases such as hepatitis and cirrhosis and conditions associated with increased RBC destruction (hemolytic anemia). When urine urobilinogen is low or absent in a patient with urine bilirubin and/or signs of liver dysfunction, it can indicate the presence of hepatic or biliary obstruction.
Bilirubin fractions present in blood and urine
Unconjugated:
Albumin-bound in serum
Measured as indirect-reacting bilirubin
Never present in urine
Conjugated:
Unbound in serum
Measured as direct-reacting bilirubin
Present in urine
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