Male Left Medial Liver Segment, Anterior View

Description

Centered in an anterior hepatic view, the left medial segment (Couinaud segment IV) occupies the medial portion of the left functional lobe, lying immediately to the left of the gallbladder fossa and just inferior to the diaphragmatic dome. Its lateral boundary aligns with the plane of the falciform ligament and the fissure for the ligamentum teres, while its medial extent approaches the midline near the fissure for the ligamentum venosum and the porta hepatis. Superiorly it abuts the left hemidiaphragm; inferiorly it contributes to the anterior aspect of the visceral surface near the hepatic margin. Orientation is clean and direct. Segment IV matters because it sits at the junction of left and right hemilivers in functional anatomy, so resection planning hinges on where you draw the middle hepatic vein plane and how you interpret the umbilical fissure. Lesions here often straddle surgical territories, and ablation or segmentectomy must respect inflow from the left portal vein (umbilical portion) and potential proximity to the hilar plate and bile ducts. This anterior perspective also helps clarify why segment IV is commonly discussed as IVa (superior) and IVb (inferior) in operative reports and cross sectional imaging correlation. Use this illustration for hepatobiliary surgery teaching on Couinaud segmentation, for radiology atlases aligning surface landmarks with CT and MRI segment maps, and for patient facing materials explaining why a “left lobe” tumor may still require a technically central resection. It also reads well in transplant and oncology publications where segment based nomenclature reduces ambiguity. Anatomical accuracy verified by SciePro's Medical Advisory Board.