Bile duct dilatation

Bile duct dilatation can be due to several aetiologies.

Clinical presentation

Variable, depending on underlying cause, but usually:

• right upper quadrant pain
• jaundice

Radiographic features

Ultrasound

Harmonic imaging is useful when assessing the biliary system, as it improves the clarity of the lumen.

• intrahepatic bile ducts
  • >2 mm
  • >40% of adjacent portal vein
• extrahepatic bile ducts (common hepatic duct and common bile duct)
  • usually measured in the proximal duct, near the hepatic artery
  • diameter measured from inner wall to inner wall
  • >6 mm +1 mm per decade above 60 years of age
  • >10 mm post-cholecystectomy
• It is common practice to refer to the common hepatic/bile duct as the common duct when reporting ultrasound, as the confluence of the cystic duct with the CHD to form the CBD is often not clearly defined.

Focal dilatation may be a result of downstream stricture, or damage to the elasticity of that segment of bile duct, possibly from prior stone passage.

Colour Doppler can be useful to ensure that dilated structures in the liver are actually bile ducts and not an intrahepatic vascular malformation.

Differential diagnosis

The second thing to establish is which part of the biliary system is dilated:

• intrahepatic
• extrahepatic
• intrahepatic and extrahepatic

Intrahepatic biliary dilatation only

• intrahepatic or hilar cholangiocarcinoma (e.g. Klatskin tumour)
• intrahepatic choledocholithiasis
• recurrent pyogenic cholangitis
• Caroli disease

Extrahepatic biliary dilatation only

• early choledocholithiasis
• sphincter of Oddi dyskinesia
• pregnancy
• choledochal cyst
• drugs (e.g. chronic opioid use) ¹

Intrahepatic and extrahepatic biliary dilatation

• pancreatic or ampullary mass (e.g. pancreatic ductal adenocarcinoma)
  • often also dilated main pancreatic duct
• choledocholithiasis
• pancreatitis
  • ​chronic pancreatitis: pancreatic atrophy, calcification, pancreatic duct dilatation seen as a “chain of lakes”
• external compression (e.g. Mirizzi syndrome, adenopathy)
• ascending cholangitis
• recurrent pyogenic cholangitis
• sclerosing cholangitis
• AIDS cholangiopathy
• choledochal cyst, type IV (rare)