Ultrasonography of dilated bile ducts

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Author: Mikael Häggström [notes 1]


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


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.[1]

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

Further workup

In case of finding dilated bile ducts:

  • Classify the severity of dilatation:
Common bile duct diameter in adults[2]
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.


  • 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


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.


  1. Hoeffel, Christine; Azizi, Louisa; Lewin, Maité; Laurent, Valérie; Aubé, Christophe; Arrivé, Lionel; Tubiana, Jean-Michel (2006). "Normal and Pathologic Features of the Postoperative Biliary Tract at 3D MR Cholangiopancreatography and MR Imaging ". RadioGraphics 26 (6): 1603–1620. doi:10.1148/rg.266055730. ISSN 0271-5333. 
  2. Yunfu Lv, Wan Yee Lau, Haiying Wu, Shunwu Chang, NingLiu, Yejuan Li, Jie Deng (2015). "Etiological Causes of Intrahepatic and Extrahepatic Bile Duct Dilatation ". International Journal of New Technology and Research (IJNTR) 1 (8). Archived from the original. .