Direct bilirubin

[nurmd01]

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i dont understand how an increase in direct bilirubin is probably a liver disease. The liver's function is to conjugate bilirubin converting it from indirect to direct bilirubin. If there is a problem with the liver, wouldnt indirect bilirubin increase because the liver doesnt function and cannot convert indirect to direct?

 

[scoKraz4]

Enzymes/transporters may not necessarily be messed up so you still conjugate it but with damage to the liver it can cause leakage of conjugated bili due to compromised bile canaliculi. I honestly wouldn't say an increased direct would probably mean liver disease. Need other labs and symptoms.

 

[Transposony]

i dont understand how an increase in direct bilirubin is probably a liver disease. The liver's function is to conjugate bilirubin converting it from indirect to direct bilirubin. If there is a problem with the liver, wouldnt indirect bilirubin increase because the liver doesnt function and cannot convert indirect to direct?

The first system to be affected in liver disease is the transport of conjugated bilirubin out of the hepatocytes (cholestasis) via bile canaliculi which runs in between two single files of hepatocytes. This is an energy intensive process which requires a lot of ATPs (the first system to be affected in cell injury is generation of ATPs).
Later the hepatocyte injury reaches a stage where the conjugation of bilirubin is also affected thereby giving a mixed picture of (both) indirect & direct hyperbilirubinemia.