Ultrasonography of dilated bile ducts

Author: Mikael Häggström

Planning

When found at abdominal ultrasonography for another purpose, it's performed in the same session.

Detection

Borderline of a dilated perihilar bile duct (see Ultrasonography of gallstones for detailed ranges).

On ultrasonography of the biliary tract, the width of the duct is usually easiest for the perihilar bile duct (which is the region where the common hepatic duct becomes the common bile duct, at the hilum of the liver). A normal width of the perihilar bile duct can be reported as for the extrahepatic bile ducts, since it also excludes a more distal common bile duct obstruction. The common bile duct is normally up to 8 mm.

Also take a look at intrahepatic bile ducts to rule out obvious dilation.

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  Doppler ultrasonography of dilated intrahepatic bile ducts, in this case because of pancreatic cancer. The bile ducts are colorless (black) in contrast to blood vessels (portal vein near center, and hepatic artery to the right of it) which have Doppler signal.

Further workup

In case of finding dilated bile ducts:

• Classify the severity of dilatation:

Common bile duct diameter in adults

Normal	≤ 8 mm
Mild dilatation	8 – 12 mm
Moderate dilatation	12 – 16 mm
Severe dilatation	16 – 20 mm
Extremely severe dilatation	>20 mm

• Attempt to determine the distal limit of the dilation (such as by the entry of the common hepatic duct into the pancreas), or alternatively the distal limit where the dilated bile duct is no longer visible.

Intraductal gallstone in a dilated common bile duct.

If a distal limit is visible, look for wall thickening or intraductal gallstone.

Report

• Severity and quantity of dilation such as "Moderately dilated common bile duct of 14 mm."
• Even absence of visible findings at the distal limit of the dilation, or where it is no longer visible.

See also: General notes on reporting