Urobilinogen / Bilirubin

• Both bilirubin and urobilinogen may be detected in urine.

• Partial or complete biliary obstruction or liver damage may cause bilirubinuria. 
The excreted bilirubin is conjugated.

• Urinary urobilinogen may be increased in hepatocellular diseases, but is not affected by partial biliary obstruction and may be decreased with complete obstruction.

• Haemolysis causes increased conjugation of bilirubin with glucuronic acid in the liver. 
The conjugated bilirubin is excreted into the bile where it is metabolized to stercobilinogen and urobilinogen. 
Some of the urobilinogen reabsorbed from the gastrointestinal tract is subsequently excreted in the urine.

• Increased urobilinogen in urine therefore occurs in:

1) Excessive RBC breakdown

2) Re-absorption - a large hematoma

3) Hepatocellular damage