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

Figure 3 Type Ia classification: Bilateral cranial-caudal trunk type of segment 4. A-D: Axial contrast-enhanced computed tomography images from a representative type Ia case, showing two dominant Glissonean trunks-Glissonean pedicles of segment 4 (G4; G4a and G4b)-supplying the cranial and caudal subsegments of segment 4 (S4), respectively. Two intermediate branches (IBs; IB1 and IB2) are also visible in panel A, arising near the bifurcation of segment 3 and S4; E: Three-dimensional portal vein reconstruction highlighting the bifurcated G4a and G4b pedicles supplying distinct cranial and caudal territories of S4; F: Schematic diagram illustrating the spatial distribution of G4a, G4b, and IBs, reinforcing the concept of bilateral cranial-caudal trunk anatomy in type Ia cases. IB: Intermediate branch; G4: Glissonean pedicles of segment 4.