Bile duct dilatation refers to the dilatation of intrahepatic or extrahepatic bile ducts.

Clinical presentation

Variable, depending on the 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)

  • properly measured in the proximal duct, either immediately below or immediately above (but not at) the crossing of the proper hepatic artery¹, which typically runs between and approximately perpendicular to the duct and the main portal vein. This portion of the duct is usually common hepatic duct^1,5 and sometimes common bile duct, since the insertion of the cystic duct is variable.

  • diameter measured from inner wall to inner wall

  • the old dictum that normal is under 6 mm (+1 mm per decade) above 60 years of age is no longer believed to be true.^1,2,3,5 Only about 1 mm total (or less) can be ascribed to advanced age.^1,5,6 Therefore, a diameter above 7.0 mm when the gallbladder is still present is abnormal.^1,5,6

  • the old dictum of >10 mm post-cholecystectomy is likewise no longer believed to be true.² A diameter above 8.0 mm post-cholecystectomy is abnormal.^1,2,3

• it is common practice to refer to the duct as the common duct (CD) or the common bile duct (CBD) when reporting ultrasound (it should be noted that anatomically there is another structure called the common duct, formed by the confluence of the common bile and pancreatic ducts). While the duct being measured, the proximal duct near hepatic artery crossing, is often referred to as the "CBD," it actually usually is the common hepatic duct, as noted above.

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

Color 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 tumor)

• intrahepatic choledocholithiasis

• recurrent pyogenic cholangitis

• Caroli disease

• portal biliopathy

• biliary necrosis

Extrahepatic biliary dilatation only

• early choledocholithiasis

• sphincter of Oddi dyskinesia

• pregnancy

• choledochal cyst

• drugs (e.g. chronic opioid use ⁴)

• commonly the residua of past, greater dilatation due to past obstruction

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)

• portal biliopathy

• ascending cholangitis

• recurrent pyogenic cholangitis

• sclerosing cholangitis

• AIDS cholangiopathy

• choledochal cyst: type IV (rare)