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.