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Topic

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Liver Segment II – Left lateral superior segment

The left lateral superior segment (Segment II) is part of the left hepatic lobe according to Couinaud’s classification. It lies in the superior and lateral aspect of the left lobe, above the level of the portal vein bifurcation, extending to the dome of the diaphragm. Segment II is bounded inferiorly by Segment III (left lateral inferior segment), medially by Segment IV (left medial lobe), and posteriorly by the left hepatic vein and ligamentum venosum.

It is drained by the left hepatic vein, which separates it from the medial segments of the left lobe. Segment II is clinically important in hepatic resections, transplant donor surgery, oncology, and interventional radiology, as it is a frequent site of metastases and primary tumors due to its peripheral location.

Synonyms

  • Segment II of liver

  • Left lateral superior segment

  • Superior portion of left lateral section

Function

  • Performs all primary liver functions: metabolism, detoxification, protein synthesis, and bile production

  • Participates in portal circulation processing of nutrients from the gastrointestinal tract

  • Plays a role in surgical liver partitioning, especially in left lateral segmentectomy (Segments II + III)

Nerve Supply

  • From the hepatic plexus:

    • Parasympathetic fibers from the vagus nerve

    • Sympathetic fibers from the celiac plexus

Arterial Supply

  • Branches of the left hepatic artery (from the proper hepatic artery)

Venous Drainage

  • Portal inflow: left portal vein (specifically the superior branch)

  • Hepatic venous outflow: drained primarily by the left hepatic vein, which empties into the IVC

MRI Appearance and Signal

T1-weighted images:

  • Segment II shows intermediate signal intensity, 

  • Surrounding fat planes and diaphragm help define borders

T2-weighted images:

  • Normal parenchyma shows intermediate to mildly hyperintense signal

  • Pathologies such as cysts and edema are bright hyperintense

STIR:

  • Fat suppression enhances lesion detection

  • Highlights edema, inflammatory changes, or infiltrative disease

T1 Fat-Saturated (Pre-contrast):

  • Segment II parenchyma shows intermediate signal

  • Stands out clearly against suppressed perihepatic fat

T1 Fat-Saturated Post-Contrast (Dynamic Gadolinium):

  • Arterial phase: homogeneous enhancement with hepatic arterial flow

  • Portal venous phase: matches the rest of liver parenchyma

  • Delayed phase: uniform attenuation unless lesion present

  • Lesions (HCC, metastases, hemangiomas) show characteristic enhancement patterns

MRI Non-Contrast 3D Imaging:

  • Provides 3D mapping of segmental anatomy, borders, and vascular supply

  • Critical for surgical planning and donor liver evaluation

Triple-Phase MRI (Dynamic Contrast):

  • Arterial phase: highlights hypervascular lesions (HCC, NET mets) in Segment II

  • Portal venous phase: hypovascular lesions (mets, cholangiocarcinoma) better seen

  • Delayed phase: fibrosis and cholangiocarcinoma show persistent enhancement

CT Appearance

CT Pre-Contrast:

  • Segment II appears isoattenuating with rest of liver parenchyma

  • Borders defined by fissure of ligamentum venosum and diaphragm

CT Post-Contrast (Single Phase):

  • Enhances uniformly with other liver tissue

  • Pathologic lesions become visible depending on vascularity

Triple-Phase CT (Liver Protocol):

  • Arterial phase: segment enhances with hepatic arterial inflow; hypervascular tumors appear bright

  • Portal venous phase: 

  • Portal vein lumen (post-contrast): bright, homogeneous enhancement.

  • Parenchyma of Segment II in portal venous phase (contrast MRI & CT): homogeneous enhancement, iso to rest of liver.

  • Delayed phase: normal tissue washes out uniformly; fibrosis and some metastases persist as hyperdense foci

CT image

Liver left lateral inferior segment — Segment II CT axial anatomy image

CT image

Liver Segment II – Left lateral superior segment CT axial anatomy image

MRI image

Liver Segment II – Left lateral superior segment MRI axial anatomy image