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Liver Biochemistry
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Liver Biochemistry

Bilirubin

  • Pigment derived as breakdown product of haem moiety
  • Produced at sites of RBC destruction
  • Circulates in blood as unconjugated, water-insoluble bilirubin bound to albumin
  • Conjugated to glucuronic acid in liver -> water soluble form
  • Excreted in bile -> GI tract
  • Bacteria in tract convert it to stercobilinogen which may be
    • absorbed and subsequently re-excreted in bile (entero-hepatic circulation)
    • absorbed and subsequently excreted in urine as urobilinogen (trace only)
    • or oxidized to stercobilin = fæcal pigment

Interpretation of changes in bilirubin concentrations

Plasma concentrations >35 µmol/l = jaundice

May be due to

Prehepatic Causes
these lead to the profile of

  • unconjugated hyperbilirubinaemia
  • normal urobilinogen
  • normal stercobilin
and occur when there is

  • excess production eg. hæmolysis
  • failure of uptake eg. Gilbert's
  • failure of conjugation eg. Crigler-Najjar

Intrahepatic Causes
these produce

  • mixed conjugated + unconjugated hyperbilirubinaemia
  • eg Hepatitis

Posthepatic Causes
these lead to profile of

  • conjugated hyperbilirubinaemia
  • high urobilinogen
  • low stercobilin
and are caused by

Liver Enzymes

  • ALT - Alanine aminotransferase
  • AST - Aspartate aminotransferase
  • gamma GT - g-Glutamyltransferase
  • Alkaline phosphatase

Albumin

Clotting Factors