Urobilinogeeni

Urobilinogen is a colorless compound produced in the intestine when gut bacteria reduce conjugated bilirubin, a breakdown product of heme excreted into bile. Conjugated bilirubin enters the gut via bile, where intestinal bacteria convert part of it to urobilinogen.

A portion of urobilinogen is reabsorbed from the gut into the portal circulation, reaches the liver, and may be excreted into bile again or pass into the systemic circulation. From there, some urobilinogen is filtered by the kidneys and appears in urine. In the intestine, urobilinogen can be oxidized to urobilin, and ultimately to stercobilin, both of which contribute to the coloration of stool.

Normal levels: small amounts of urobilinogen are normally present in urine. Urine testing for urobilinogen is commonly performed as part of urinalysis, typically using dipstick or laboratory assays. The test result can aid in assessing bilirubin metabolism and liver–biliary function.

Clinical significance: urinary urobilinogen levels help distinguish between different patterns of bilirubin handling. Increased urinary urobilinogen may occur with higher bilirubin production or with hepatic dysfunction that allows more urobilinogen to escape hepatic clearance. Decreased or absent urinary urobilinogen can occur with biliary obstruction or conditions that suppress gut bacterial conversion of bilirubin. The combined assessment of urinary urobilinogen and bilirubin helps differentiate obstructive from hepatocellular disorders and informs evaluation of hemolysis or liver disease.