Ventral Presentation of the Left Medial Division of the Male Liver

Description

Anterior inspection centers on the left medial division of the liver (Couinaud segment IV), positioned to the left of the gallbladder fossa and immediately medial to the left lateral division (segments II and III). Superiorly it abuts the visceral surface beneath the diaphragm, while inferiorly it approaches the free margin where the quadrate lobe (classically described as part of the left lobe) lies between the fissure for the ligamentum teres and the fossa for the gallbladder. Medial and posterior relationships bring the caudate lobe (segment I) into view near the porta hepatis, with the fissure for the ligamentum venosum marking the boundary toward the left hepatic vein territory. Clean segmental landmarks. Segment IV matters because it sits at the crossroads of portal inflow, hepatic venous drainage, and common surgical planes used in left hepatectomy and extended right hepatectomy, where the line of demarcation often tracks along the Cantlie line toward the middle hepatic vein. Lesions in segment IV, including hepatocellular carcinoma or colorectal liver metastases, frequently challenge margin planning because they lie close to the hilum and biliary confluence, raising the stakes for bile leak and ischemic injury if segmental pedicles are misidentified. This ventral presentation clarifies why the quadrate region is a surface description, while segment IV is a functional unit defined by portal pedicles. Use this illustration in gross anatomy and hepatobiliary surgery teaching to reinforce Couinaud segmentation, classic lobe terminology (quadrate, caudate), and the practical location of segment IV for operative planning, radiology correlation, and atlas publication figure plates. It also suits patient education materials for segmental liver resection when paired with axial CT or MRI examples. Anatomical accuracy verified by SciePro's Medical Advisory Board.