Urobilinogen is a colourless compound formed in the intestines when bacteria break down bilirubin excreted in bile. Some is reabsorbed and returns to the liver; a small amount escapes into the bloodstream and is excreted in urine.
Small amounts in urine are normal. Elevated urobilinogen indicates haemolysis or liver disease. Absent urobilinogen suggests complete bile duct obstruction, where bilirubin never reaches the intestines. It is a standard component of routine urinalysis.
FAQs
How does urobilinogen differ from bilirubin in urine?
Urine bilirubin indicates conjugated bilirubin spilling directly from liver disease or obstruction. Urobilinogen reflects the downstream recycling pathway in the intestine, elevated with haemolysis or liver disease and absent with complete obstruction. The two tests together help classify the type of jaundice.
Can urobilinogen be elevated without jaundice?
Yes. Mild haemolysis or early liver disease can elevate urobilinogen before bilirubin is high enough to cause clinical jaundice. Urobilinogen can be an early screening indicator.
Why is urobilinogen absent in complete obstruction?
Bilirubin cannot reach the intestine if the bile duct is completely blocked. Without intestinal bacteria converting bilirubin to urobilinogen, none is produced or reabsorbed, making urine and stool both absent in urobilinogen (pale stools are a classic sign).
What are the units for urobilinogen?
Urobilinogen is typically expressed as Ehrlich units per decilitre (EU/dL) or mg/dL. Trace to 1+ is normal; above 1 EU/dL is elevated.
