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Left branch of portal vein

The left branch of the portal vein (LPV) is one of the two major intrahepatic divisions of the main portal vein. After the main portal vein bifurcates at the hepatic hilum, the LPV courses horizontally and anteriorly toward the left hepatic lobe. It gives rise to branches that supply segments II, III, and IV of the liver.

The LPV plays a key role in directing nutrient-rich blood from the gastrointestinal tract and spleen into the left hepatic lobe, enabling metabolic processing, detoxification, and hepatocyte perfusion. Its predictable anatomy is critical for hepatic surgery, transplant planning, segmental resections, interventional radiology, and oncologic mapping.

Synonyms

  • Left portal vein

  • Left intrahepatic portal branch

  • Left hepatic portal ramus

Location and Structure

  • Position: Travels in the left portion of the portal triad within the hepatoduodenal ligament and then into the left hepatic lobe.

  • Orientation: Courses horizontally, then ascends and curves anteriorly (“umbilical portion”).

  • Umbilical fissure: The anterior curved portion communicates with paraumbilical veins.

  • Branches:

    • Segment II branch

    • Segment III branch

    • Segment IV branch (medial left lobe)

Relations

  • Anteriorly: Left hepatic duct and hepatic artery branches

  • Posteriorly: Caudate lobe (segment I)

  • Superiorly: Left hepatic parenchyma and falciform ligament region

  • Inferiorly: Left hepatic biliary channels

  • Medially: Ligamentum teres and ligamentum venosum at umbilical portion

  • Laterally: Left lateral segments (II and III)

Branches

  • Segment II portal branch

  • Segment III portal branch

  • Segment IV portal branches (IVA and IVB)

  • Paraumbilical venous communications via the umbilical fissure

Function

  • Delivers oxygenated and nutrient-rich blood to the left hepatic lobe

  • Supports liver metabolic functions including glucose storage, detoxification, and protein synthesis

  • Essential for segmental perfusion, guiding surgical planning and resection boundaries

  • Maintains hepatopetal flow that contributes to normal hepatic function

Clinical Significance

  • Key structure in liver transplant anatomy, especially left-lobe grafts

  • Crucial for segment II–III resections, left hepatectomy, and tumor mapping

  • Site for portal vein embolization (PVE) to induce right lobe hypertrophy

  • Important in imaging evaluation for portal vein thrombosis, tumor invasion, cirrhosis-related remodeling, and cavernous transformation

  • Close proximity to the umbilical fissure allows communication with paraumbilical collaterals in portal hypertension

MRI Appearance

MRV TOF (Time-of-Flight Venography)

  • LPV appears as a bright, high-signal vascular structure due to flowing blood

  • Clearly delineates the left portal bifurcation and umbilical portion

  • Helps assess patency, stenosis, and directional flow

  • Thrombus or absent flow appears signal void

T1 Fat-Saturated GRE

  • Flowing blood: Low signal (signal void)

  • Portal vein wall: Thin, low-to-intermediate signal

  • Surrounding liver parenchyma: Intermediate T1 signal, brighter with fat saturation

  • Portal lumen: Typically dark unless flow is slow

  • Umbilical portion: Smooth linear low-signal vessel along fissure

T2-weighted images

  • LPV lumen shows low-to-intermediate signal depending on flow rate

  • High-flow segments appear darker (flow void)

  • Liver parenchyma is intermediate-to-bright T2 signal

  • Surrounding bile ducts appear hyperintense relative to portal lumen

Post-Contrast T1 Fat-Saturated GRE

  • LPV enhances rapidly and uniformly in the portal venous phase

  • Clear visualization of branches to segments II–IV

  • Umbilical portion enhances consistently along its length

  • Provides excellent assessment of vessel caliber, patency, and perfusion symmetry

CT Appearance

Post-Contrast CT (Portal Venous Phase)

  • Left portal vein shows homogeneous contrast enhancement

  • Easily visible as a branching, well-opacified structure within the left hepatic lobe

  • Allows detailed assessment of:

    • Segmental branching to II, III, IV

    • Vessel diameter and course

    • Relationship to hepatic fissures and tumors

  • Umbilical portion enhances, seen adjacent to ligamentum teres

  • High-resolution depiction of portal venous anatomy essential for surgical planning

MRI images

Left branch of portal vein CT axial image-img-00000-00000