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Bile duct serving liver segment II

The bile duct serving liver segment II is a segmental intrahepatic duct that drains bile from the superior part of the left lateral sector of the liver. It is part of the left hepatic biliary system and is a key structure in both anatomic liver resections and biliary imaging. It contributes to the formation of the left hepatic duct after joining with the duct from segment III.

Because segment II lies in the superior portion of the left lobe, its duct runs medially and slightly inferiorly before merging with other left-sided ducts. Understanding its anatomy is crucial for surgical planning, especially in segmental liver resection, transplantation, and biliary reconstruction.

Synonyms

  • Segment II bile duct

  • Superior left lateral sectoral bile duct

  • Intrahepatic bile duct of segment II

Origin, Course, and Termination

  • Origin: Collects bile from canaliculi and interlobular ducts of Couinaud’s segment II (superior lateral segment of left lobe).

  • Course: Runs medially through the superior part of the left lobe toward the umbilical portion of the left portal fissure.

  • Termination: Joins the bile duct of segment III to form the left hepatic duct, which later contributes to the common hepatic duct.

Relations

  • Anteriorly: Superior liver capsule and diaphragm

  • Posteriorly: Left portal vein branch supplying segment II

  • Laterally: Liver parenchyma of segment II

  • Medially: Joins segment III duct near the umbilical fissure

Function

  • Collects bile from hepatocytes of segment II

  • Transports bile toward the left hepatic duct and ultimately into the common hepatic duct

  • Plays a role in segmental drainage important for resectional surgery and transplantation

Clinical Significance

  • Liver transplantation: Segment II duct is important in left lateral segment (segments II & III) grafts, commonly used in pediatric liver transplants

  • Surgical resections: Injury or misidentification of the segment II duct may cause bile leaks or strictures

  • Cholangiopathies: May be involved in intrahepatic cholangitis, stones, or strictures

  • Tumors: Cholangiocarcinoma or hepatocellular carcinoma may obstruct the duct

  • MRCP imaging: Important for segmental mapping of intrahepatic biliary tree

MRI Appearance

T1-weighted images:

  • Bile duct lumen: dark (low signal)

  • Duct wall: thin, low signal; may enhance post-contrast

T2-weighted images:

  • Lumen: bright (high signal)

  • Wall: thin, dark outline

STIR (Short Tau Inversion Recovery):

  • Bile fluid: bright hyperintensity

  • Fat suppressed → better visualization of duct against parenchyma

T1 Fat-Sat Post-Contrast:

  • Normal wall: minimal or no enhancement

  • Pathology: duct wall thickening or enhancing strictures

T2 Fat-Saturated HASTE (single-shot):

  • Duct lumen: bright signal, sharply visualized

  • Stones: dark filling defects within bright duct lumen

  • Rapid sequence, ideal for screening

T2 TSE Fat-Saturated 3D (MRCP):

  • High-resolution 3D dataset of bile ducts

  • Duct appears bright, continuous with segment III duct and left hepatic duct

  • Useful for preoperative mapping of segmental biliary anatomy

Thick-slab T2 Fat-Saturated HASTE:

  • Projectional MRCP image shows duct as a bright tubular structure draining into left hepatic duct

  • Filling defects (stones, air bubbles) appear dark within bright lumen

CT Appearance

Non-Contrast CT:

  • Duct usually not visible unless dilated

  • Dilated duct: low attenuation tubular structure in segment II

  • Stones: hyperdense if calcified

Post-Contrast CT:

  • Normal duct: no significant enhancement

  • Wall enhancement seen in cholangitis, cholangiocarcinoma, or inflammation

  • Dilated ducts stand out as non-enhancing tubular structures against enhancing liver parenchyma

MRI image

Bile duct serving liver segment II MRI axial anatomy image-img-00000-00000