Revisiting the Intersegmental Plane in Anatomical Liver Resection: A Three-Zone Framework Beyond Hepatic Vein Exposure.

Accurate identification of the intersegmental plane is critical for anatomical liver resection (ALR), which aims to remove hepatic segments based on portal venous territories. Traditionally, hepatic veins have served as the primary landmark for these planes. However, advances in 3D reconstruction and indocyanine green (ICG) fluorescence imaging reveal that true portal territory boundaries often deviate from hepatic vein trajectories. We propose a three-zone classification of intersegmental planes based on their spatial relationship with the hepatic veins to guide surgical strategy. Zone 1 (Exposure Zone): The plane runs alongside a major hepatic vein, providing a clear landmark but requiring precise dissection to avoid venous injury. Zone 2 (Crossing Zone): The plane intersects a hepatic vein or its branches, creating the highest risk of bleeding due to unexpected venous crossings. Zone 3 (No Exposure Zone): The plane lies entirely within the parenchyma, away from major veins, making bleeding minimal but requiring ICG guidance to avoid disorientation. Intersegmental planes should be conceptually defined as Glissonean-free watersheds rather than solely by hepatic vein location. This zone-based classification provides a practical framework for preoperative planning and intraoperative decision-making, allowing surgeons to anticipate venous exposure and optimize dissection techniques for safer, more precise ALR.