Bile duct dilatation
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Bile duct dilatation refers to the dilatation of intrahepatic or extrahepatic bile ducts.
Variable, depending on the underlying cause, but usually:
right upper quadrant pain
Harmonic imaging is useful when assessing the biliary system, as it improves the clarity of the lumen.
intrahepatic bile ducts
>40% of adjacent portal vein
usually measured in the proximal duct, near the proper 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 2
it is common practice to refer to the common hepatic/bile duct as the common duct (CD) when reporting ultrasound, as the confluence of the cystic duct with the common hepatic duct (CHD) to form the common bile duct (CHD) is often not clearly defined.
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.
The second thing to establish is which part of the biliary system is dilated:
intrahepatic and extrahepatic
Intrahepatic biliary dilatation only
Extrahepatic biliary dilatation only
drugs (e.g. chronic opioid use) 1
Intrahepatic and extrahepatic biliary dilatation
often also dilated main pancreatic duct
external compression (e.g. Mirizzi syndrome, adenopathy)
choledochal cyst: type IV (rare)