Why is urine urobilinogen increased in unconj bilirubinemia?

[bonoz]

I thought only conjugated bilirubin could be converted to urobilinogen in the gut and thus make its way into the urine? Why is unconj bilirubinemia causing increased urine urobilinogen?

I get that it is low in conjugated because due to obstruction keeping CB reaching gut and thus keeping it from getting converted to urobilinogen.

Thanks

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[SBR249]

Unconjugated bilirubinemia does not automatically mean the conjugation/excretion process is defective. It could just be that the patient has hemolysis and that the extra bilirubin generated saturates the conjugation/excretion pathway and accumulates behind the bottleneck. In that case, you'd have increased levels of conjugated bilirubin reaching the GI tract leading to increased urobilinogen product and uptake by the enterohepatic circulation.

 

[GlowInTheDark]

Unconjugated bilirubinemia does not automatically mean the conjugation/excretion process is defective. It could just be that the patient has hemolysis and that the extra bilirubin generated saturates the conjugation/excretion pathway and accumulates behind the bottleneck. In that case, you'd have increased levels of conjugated bilirubin reaching the GI tract leading to increased urobilinogen product and uptake by the enterohepatic circulation.

This is particularly high-yield for purposes of board examination.

 

[bonoz]

Ah! That makes perfect sense. Thanks.

 

[NeuroLAX]

This is particularly high-yield for purposes of board examination.

I see what you did there. The pathway is Sattarated!