Portal vein-based subsegmental classification of liver segment four for parenchyma-sparing laparoscopic resection: A retrospective study

Figure 1 Portal territory-defined boundaries of segment 4 based on intermediate branches. A-D: Axial contrast-enhanced computed tomography images showing intermediate branches (IBs; orange arrows) arising between the Glissonean pedicles of segments 3 and 4, supplying liver parenchyma on both sides of the falciform ligament; E and F: Three-dimensional reconstruction images demonstrating bilateral perfusion territories of the IBs, extending across the falciform ligament; G: Intraoperative laparoscopic view confirming the presence of IB during hepatic dissection; H: Schematic illustration of the traditional anatomical segment 4 (S4) boundary, with the left margin defined by the falciform ligament; I: Portal territory-based redefinition of the S4 territory showing leftward extension beyond the falciform ligament, in line with IB perfusion; J: Refined anatomical boundary of S4 according to the proposed portal vein-based classification, encompassing the full extent of perfused parenchyma. IB: Intermediate branch; G2: Glissonean pedicles of segment 2; G3: Glissonean pedicles of segment 3; G4: Glissonean pedicles of segment 4.