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Left hepatic duct

The left hepatic duct is a major intrahepatic bile duct that drains bile from the left lobe of the liver, including the medial and lateral segments (segments II, III, and IV of Couinaud’s classification). It runs from the left hepatic hilum to the porta hepatis, where it unites with the right hepatic duct to form the common hepatic duct.

It is a key structure in hepatobiliary anatomy, radiology, and surgery, particularly in liver transplantation, biliary drainage procedures, and evaluation of obstructive jaundice.

Synonyms

  • Left main hepatic duct

  • Left extrahepatic bile duct (proximal portion)

  • Left biliary channel

Origin, Course, and Termination

  • Origin: Formed by the union of segmental ducts draining the left medial (segment IV) and left lateral sectors (segments II and III) of the liver

  • Course: Runs horizontally and slightly obliquely from the left hepatic hilum within the hepatoduodenal ligament, anterior to the left branch of the portal vein

  • Termination: Joins the right hepatic duct at the porta hepatis to form the common hepatic duct

Relations

  • Anteriorly: Peritoneum of hepatoduodenal ligament

  • Posteriorly: Left branch of the portal vein

  • Superiorly: Left lobe of the liver parenchyma

  • Inferiorly: Left hepatic artery and its branches

Function

  • Collects and conveys bile from the left hepatic segments (II, III, IV)

  • Joins with right hepatic duct to continue bile flow into the extrahepatic biliary system

  • Provides a crucial surgical and imaging landmark in liver resections, transplantation, and biliary interventions

Clinical Significance

  • Obstruction: Gallstones, strictures, or cholangiocarcinoma may cause left-sided intrahepatic biliary dilatation

  • Liver transplant: Accurate identification of left hepatic duct anatomy is critical for biliary anastomosis

  • Variants: Biliary anatomical variants are common (trifurcation, low insertion), important for surgery and radiology

  • Infection: Ascending cholangitis may involve this duct

  • Intervention: Accessed in percutaneous biliary drainage for left-sided biliary obstruction

MRI Appearance

T1-weighted images:

  • Lumen appears dark (low signal) due to bile fluid

  • Wall is thin, sometimes imperceptible; enhances slightly with contrast

T2-weighted images:

  • Lumen: bright (high signal) due to bile fluid

  • Wall: thin hypointense rim

STIR (Short Tau Inversion Recovery):

  • Bile remains bright

  • Fat signal suppressed, improving duct contrast

T1 Fat-Sat Post-Contrast:

  • Wall enhances subtly if normal

  • Pathology (strictures, infection, tumor): wall thickening or irregular, enhancing masses

T2 Fat-Saturated HASTE (single-shot):

  • Left hepatic duct: appears as a bright tubular structure

  • Excellent for rapid screening of obstruction, stricture, or stones

  • Stones: dark filling defects within bright fluid lumen

T2 TSE Fat-Saturated 3D (MRCP sequence):

  • Provides high-resolution 3D dataset of the entire biliary tree

  • Left hepatic duct visualized as a bright tubular channel joining right hepatic duct

  • Excellent for evaluating strictures, variants, and pre-surgical mapping

Thick-slab T2 Fat-Saturated HASTE:

  • Shows left hepatic duct as part of the biliary tree in a projectional MRCP image

  • Highlights duct continuity and filling defects (stones, air bubbles) as dark voids against bright fluid

CT Appearance

Non-Contrast CT:

  • Duct not easily visible unless dilated

  • Dilated duct: seen as low-attenuation tubular structure within liver parenchyma

  • Stones: calcified stones appear hyperdense; non-calcified stones may be occult

Post-Contrast CT:

  • Wall enhances faintly

  • Dilated ducts appear as low-density channels with enhancing wall

  • Pathology: strictures (narrowing), cholangiocarcinoma (enhancing soft tissue lesion), inflammatory wall thickening

MRI image

Left hepatic duct mri axial anatomy image-img-00000-00000

MRI image

Left hepatic duct mri coronal anatomy image-img-00000-00000_00001