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Portal vein branch to liver segment III

The portal vein branch to liver segment III is a segmental intrahepatic branch of the left portal vein that specifically supplies Couinaud segment III, located in the inferior portion of the left lateral section of the liver. After arising from the left portal vein, it runs laterally and inferiorly within the liver parenchyma to distribute blood to the parenchymal plates of segment III.

This branch delivers nutrient-rich venous blood from the gastrointestinal tract to hepatocytes in segment III, complementing the hepatic arterial inflow. Venous blood from segment III drains through corresponding hepatic venules into the left hepatic vein, which empties into the inferior vena cava (IVC).

Clinically, the segment III portal branch is significant in hepatic surgery, segmental resections, living donor liver transplantation, and interventional radiology. Precise mapping of segmental portal branches is crucial to ensure preservation of vascular inflow and to avoid ischemia during partial hepatectomy.

Synonyms

  • Segment III portal vein branch

  • Portal branch to left lateral segment (inferior)

  • Intrahepatic portal branch to Couinaud segment III

Function

  • Provides nutrient-rich venous inflow from gastrointestinal tract to hepatocytes of segment III

  • Ensures coordinated dual blood supply (with left hepatic artery branch)

  • Serves as a surgical and radiological landmark for left lateral liver resections

MRI Appearance

T1-weighted images:

  • Branch appears as a signal void (dark tubular structure) within segment III parenchyma

  • Surrounded by intermediate liver tissue

T2-weighted images:

  • Vessel lumen remains a dark flow void

  • Adjacent pathology (e.g., edema or infiltration) appears hyperintense, outlining vessel course

STIR:

  • Suppresses fat signal, making the vessel more conspicuous against suppressed parenchyma

  • Highlights perivascular inflammatory changes if present

T1 Fat-Saturated (Pre-contrast):

  • Lumen demonstrates intermediate signal intensity, contrasting with suppressed fat and parenchymal background

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Segment III branch enhances brightly in the portal venous phase

  • Visualizes segmental perfusion of left lateral inferior parenchyma

MRV (Magnetic Resonance Venography):

  • Provides detailed mapping of left portal vein and its segmental branches

  • Demonstrates course and drainage territory of segment III branch

  • Critical in donor evaluation, hepatic surgery, and pre-interventional planning

CT Appearance

CT Pre-Contrast:

  • Portal branch appears as a small tubular soft-tissue density within segment III parenchyma

  • Poorly visualized without contrast

CT Post-Contrast:

  • Enhances during portal venous phase, showing clear course into segment III

  • Early enhancement aids differentiation from hepatic arteries in arterial phase

CTV (CT Venography):

  • Gold standard for visualizing intrahepatic portal branches

  • 3D reconstructions show portal inflow to segment III, with clear visualization of vascular territory

  • Essential in segmentectomy planning, transplantation, and embolization procedures

CT images

Portal vein branch to liver segment III axial CT image

CT images

Portal vein branch to liver segment III