Why do you need to conjugate bilirubin?

[nm825]

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1. Why do you need to conjugate bilirubin? From what I understand, hepatocytes take up unconjugated from blood and conjugate it. They then excrete into the bile canals. It is then secreted in the bile after feeding. Upon entering the gut, it is unconjugated and formed into urobilinogen. 90% of this then leaves in the stool. Some of the urobilinogen is taken back up into the systemic circulation and excreted by the kidney.

What is the point of conjugating the bilirubin to make it water-soluble? Why does it need to be water soluble?

2. Also, why do you see mixed conjugated and unconjugated in advanced hepatitis? Is it because the damage hepatocytes lose their ability to conjugate effectively and at the same time can't excrete the conjugated bilirubin into the canals properly?

 

[Jabbed]

1. Because kernicterus.
2. Hepatitis is associated with hepatic AND intra-hepatic biliary disease. ↓conjugation → ↑UCB; ↓excretion → ↑CB

 

[slz1900]

My understanding, and I apologize if I am wrong, is that it needs to be water soluble to be excreted into the bile unbound to a protein. Secondly, unconjugated bilirubin will be absorbed in the gut, so it needs to be conjugated in order to reach the colon where it can be metabolized to urobilinogen by bacteria.