Podcast
Questions and Answers
What is the primary substance formed from free bilirubin in the colon?
What is the primary substance formed from free bilirubin in the colon?
What is the normal output range of urobilinogen in urine over 24 hours?
What is the normal output range of urobilinogen in urine over 24 hours?
In which condition is the output of urobilinogen in urine most likely increased?
In which condition is the output of urobilinogen in urine most likely increased?
Which of the following describes urobilinogen?
Which of the following describes urobilinogen?
Signup and view all the answers
What effect does alkaline urine have on urobilinogen output?
What effect does alkaline urine have on urobilinogen output?
Signup and view all the answers
Study Notes
Urobilinogen in Urine
- Conjugated bilirubin, complexed with cholesterol, bile salts, and phospholipids, travels to the duodenum via bile.
- Bacteria in the colon hydrolyze the conjugated bilirubin, reducing it to urobilinogen, mesobilirubinogen and stercobilinogen.
- Up to 50% of urobilinogen is reabsorbed into the portal circulation, then re-excreted into bile, in an unconjugated form.
- Most of the remaining urobilinogen is excreted via the feces as colored urobilins or stercobilin (after further hydrogen removal).
- A small amount of urobilinogen is excreted in urine.
- Urobilinogen is measured in "units" (roughly equivalent to milligrams per deciliter), as it represents a mixture of compounds.
Normal Levels
- Normal urine urobilinogen output is 0.5–2.5 mg or units per 24 hours.
- Urobilinogen is colorless and unstable (labile), contrasting with urobilins (its oxidized form), which give urine its yellow-orange hue.
Factors Influencing Urobilinogen Excretion
- Alkaline urine increases urobilinogen excretion.
- Acidic urine decreases urobilinogen excretion.
- Elevated levels in the urine indicate liver issues, such as impaired removal from the portal circulation.
Liver Dysfunction and Urobilinogen
- Hepatocellular damage (viral hepatitis, drugs, toxins, or cirrhosis) can result in increased urobilinogen excretion as the liver struggles to remove it.
- Liver congestion (e.g., from congestive heart failure) prevents efficient urobilinogen re-excretion into bile, leading to higher urine levels.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz explores the formation, measurement, and normal levels of urobilinogen in urine. It covers the biochemical processes involving bilirubin and the factors influencing urobilinogen excretion. Test your understanding of this important metabolic compound and its significance in urine analysis.
