Bilirubin and Urobilinogen
Bilirubin is a bile pigment formed during the breakdown of hemoglobin. Normally, bilirubin is absent in urine, as it is completely processed by the liver and excreted with bile.
The appearance of bilirubin in urine (bilirubinuria) indicates liver damage or impaired bile flow. This may be observed in diseases such as liver cirrhosis, viral hepatitis, obstructive jaundice, liver tumors, and biliary tract obstruction.
Urobilinogen is a breakdown product of bilirubin, formed in the intestine under the action of bacteria. Normally, a small amount of urobilinogen is excreted in urine (up to 17 µmol/L).
An increased level of urobilinogen in urine (urobilinogenuria) may indicate hemolytic anemia, liver diseases (hepatitis, cirrhosis, toxic damage), as well as certain intestinal and cardiovascular diseases.
Decreased or absent urobilinogen in urine may indicate biliary tract obstruction or severe liver damage.
Thus, determining bilirubin and urobilinogen in urine is an important diagnostic tool for detecting liver and biliary tract diseases, as well as hemolytic and other systemic pathologies.