Extrahepatic cholestasis results from the mechanical obstruction to large bile ducts outside the liver or within the porta hepatis.
The liver is enlarged and the intra-hepatic bile ducts widely dilated. The bile ducts proliferate in the portal zones. Infection of the bile above the obstruction leads to cholangitis; the ducts contain pus and may be surrounded by small abscesses.
The biochemical derangement is reinforced by clinical symptoms and signs:
- pale stool - no bilirubin reaching gastrointestinal tract for conversion to stercobilin
- dark orange urine - reflux of conjugated bilirubin into blood and excretion in urine