| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Urobilinogen is a colourless product of bilirubin reduction. It is formed in the intestines by bacterial action. Some urobilinogen is reabsorbed, taken up into the circulation and excreted by the kidney. This constitutes the normal "enterohepatic urobilinogen cycle".
Increased amounts of bilirubin are formed in hemolysis, which generates increased urobilinogen in the gut. In liver disease (such as hepatitis), the intrahepatic urobilinogen cycle is inhibited also increasing urobilinogen levels. Urobilinogen is converted to the yellow pigmented urobilin apparent in urine.
In biliary obstruction, below-normal amounts of conjugated bilirubin reach the intestine for conversion to urobilinogen. With limited urobilinogen available for reabsorption and excretion, the amount of urobilin found in the urine is low. High amounts of the soluble conjugated bilirubin enter 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. (Obstruction of bilirubin passage into the gut or failure of urobilinogen production in the gut.)
Elevated levels may indicate hemolytic anaemia (excessive breakdown of red blood cells), overburdening of the liver, increased urobilinogen production, re-absorption - a large hematoma, restricted liver function, hepatic infection, poisoning or liver cirrhosis.
Urobilinogen (aka d-urobilinogen) is closely related to two other compounds: mesobilirubinogen (aka i-urobilinogen) and stercobilinogen (aka i-stercobilinogen). Specifically, urobilinogen can be reduced to form mesobilirubinogen, and mesobilirubinogen can be further reduced to form stercobilinogen. Confusingly, however, all three of these compounds are frequently collectively referred to as "urobilinogens".
Urobilinogen content is determined by a reaction with Ehrlich's reagent, which contains para-Dimethylaminobenzaldehyde and may be measured in Ehrlich units. One Ehrlich unit is equal to one milligram of urobilinogen per deciliter of sample (1 mg/dL).
- "Urobilinogen". Family Health Information. Retrieved 2008-03-30.
- "Urobilinogen in urine". Home test kist. Retrieved 2008-03-30.
- "Biochemical Pathways Map No. L5 L6". ExPASy Bioinformatics Resource Portal. Retrieved 12 December 2011.
- Henry's clinical diagnosis and management by laboratory methods. (22nd ed. ed.). Philadelphia, PA: Elsevier/Saunders. p. 543. ISBN 978-1-4377-0974-2.
- Urobilinogen Information and Courses from MediaLab, Inc. Retrieved on Jan 8, 2009