A colorless product of bilirubin reduction.
Formed in the intestines by bacteria.
Urobilinogen is reabsorbed, taken up into the circulation and excreted by the kidney in the enterohepatic urobilinogen cycle.
Increased amounts of bilirubin are formed in hemolysis, which generates increased urobilinogen in the gut.
In liver disease the intrahepatic urobilinogen cycle is inhibited also increasing urobilinogen levels.
Urobilinogen is converted to the yellow pigmented urobilin apparent in urine.
The urobilinogen in the intestine is oxidized to brown stercobilin, which gives the feces their characteristic color.
In the presence of biliary obstruction, below-normal amounts of conjugated bilirubin reach the intestine for conversion to urobilinogen and limited urobilinogen is available for reabsorption and excretion, decreasing the amount of urobilin found in the urine.
In the presence of biliary obstruction with high amounts of the soluble conjugated bilirubin entering the circulation where they are excreted via the kidneys:These mechanisms are responsible for the dark urine and pale stools observed in biliary obstruction.
Low urine urobilinogen may result from complete obstructive jaundice or treatment with broad-spectrum antibiotics, which destroy the intestinal bacterial flora.
Low urine urobilinogen levels may result from congenital enzymatic jaundice syndromes or from treatment with drugs that acidify the urine.
Urobilinogen content is determined by a reaction with Ehrlich’s reagent.
Normal urobilinogen range in urine is less than 17 umol/l (< 1mg/dl).
Abnormally high urobilinogen values may indicative of impaired hepatic function, hemolysis, increased urobilinogen production, increased reabsorption of bilirubin as with a hematoma, hepatitis, poisoning, and cirrhosis.
Low levels may reflect failure of bile production or biliary obstruction.