| Bilirubin in Biliary Obstruction
Extrahepatic Obstruction
1.Causes: Stone in the common bile duct; carcinoma in the head
of the pancreas.
2.Initially causes an increase in conjugated bilirubin.
3.Later, unconjugated bilirubin increases, with stabilization of
the ratio at about 1:1 conjugated:unconjugated
Intrahepatic Obstruction
1.Causes: Multiple (hepatitis, drug/alcohol injury, active cirrhosis,
congestion, metastatic tumor).
2.Variable increase in both conjugated and unconjugated bilirubin,
so ratio differs between patients.
A relative increase in conjugated bilirubin tends to suggest some
type of obstruction; a relative increase in unconjugated bilirubin
tends to suggest increased bilirubin production or (less commonly)
hepatocellular disease.
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