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Liver Segment V – Right anteroinferior segment

Segment V is part of the right anterior sector of the liver in Couinaud’s classification. It lies inferior to the portal vein plane, beneath Segment VIII (right anterosuperior segment), and anterior to Segment VI (right posteroinferior). It extends inferiorly toward the gallbladder fossa and anterior abdominal wall, forming the anteroinferior portion of the right lobe.

Segment V is separated from:

  • Segment VI by the right hepatic vein (posteriorly)

  • Segment VIII by the horizontal plane of the right portal vein

  • Segment IV by the middle hepatic vein and main portal fissure (medially)

Its anatomical location makes it especially important in cholecystectomy, right hepatic resections, trauma surgery, and interventional radiology, since it lies adjacent to the gallbladder bed and is frequently affected by gallbladder-related pathology or metastatic disease.

Synonyms

  • Segment V of liver

  • Right anteroinferior segment

  • Subhepatic right anterior segment

Function

  • Performs all core hepatic functions: bile production, detoxification, metabolism, and protein synthesis

  • Processes blood from the gastrointestinal tract via portal inflow

  • Key region for surgeons due to its proximity to gallbladder and biliary tract

Nerve Supply

  • Hepatic plexus:

    • Parasympathetic fibers from the vagus nerve

    • Sympathetic fibers from the celiac plexus

Arterial Supply

  • Branches from the right hepatic artery (anterior division)

Venous Drainage

  • Portal inflow: anterior branch of the right portal vein (inferior division)

  • Outflow: mainly via the middle hepatic vein, draining into the IVC

MRI Appearance and Signal

T1-weighted images:

  • Segment V parenchyma shows intermediate signal intensity, iso to other liver segments

  • Gallbladder fossa fat helps define inferior border

T2-weighted images:

  • Normal parenchyma is intermediate to mildly hyperintense

  • Pathologies (cysts, hemangiomas, edema) appear markedly hyperintense

STIR:

  • Suppresses fat, making edema, infiltration, or lesions stand out as bright areas

T1 Fat-Saturated (Pre-contrast):

  • Parenchyma shows intermediate signal, highlighted against suppressed fat

  • Portal vein and hepatic vein lumens appear dark flow voids

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

  • Arterial phase: homogeneous enhancement with hepatic arterial inflow; hypervascular lesions appear bright

  • Portal venous phase: uniform parenchymal enhancement; portal vein itself enhances brightly

  • Delayed phase: homogeneous washout in normal parenchyma; fibrosis or tumors may persist enhanced

MRI Non-Contrast 3D Imaging:

  • Provides 3D mapping of Segment V relative to gallbladder fossa and hepatic veins

  • Useful for oncology planning, trauma, and donor evaluation

Triple-Phase MRI (Dynamic):

  • Arterial phase: hypervascular lesions (HCC, NET metastases) appear bright within Segment V

  • Portal venous phase: hypovascular lesions (mets, cholangiocarcinoma) become more evident against enhanced parenchyma

  • Delayed phase: scars, fibrotic tissue, and cholangiocarcinoma show persistent enhancement

CT Appearance

CT Pre-Contrast:

  • Segment V isoattenuating to liver; boundaries defined by gallbladder fossa and hepatic veins

CT Post-Contrast (Single phase):

  • Homogeneous enhancement with rest of liver parenchyma

  • Pathologies visible depending on vascularity

Triple-Phase CT (Liver Protocol):

  • Arterial phase: Segment V enhances briskly; hypervascular lesions stand out

  • Portal venous phase: parenchyma uniformly enhanced; hypovascular lesions appear hypodense

  • Delayed phase: normal parenchyma washes out evenly; fibrotic tissue and certain tumors show persistent hyperdensity

CT image

Liver right anteroinferior segment — Segment V CT image CT axial anatomy image

CT image

Liver right anteroinferior segment — Segment V CT image

MRI image

Liver right anteroinferior segment — Segment V MRI axial anatomy image