Detailed Presentation of the Left Anterior Lateral Segment of the Male Liver

Description

Positioned in the left hepatic lobe, Couinaud segment III occupies the anterior and lateral portion of the left liver, lying inferior to segment II and left of the falciform ligament and umbilical fissure. Its parenchyma sits anteroinferiorly against the diaphragmatic and visceral surfaces, approaching the left hepatic margin toward the costal arch. Segmental inflow follows the left portal vein, with third segmental (segment III) portal venous branches accompanied by hepatic arterial counterparts, while venous outflow tracks posteriorly toward the left hepatic vein within the left hepatic vein territory. Surgical planning often hinges on separating segment III from neighboring units along true segmental planes rather than external lobar contours. During laparoscopic left lateral sectionectomy or segment III segmentectomy, the surgeon typically controls Glissonian pedicles to the left lateral sector, and this targeted depiction helps distinguish segment III inflow from segment II branches and from segment IV across the umbilical fissure. Clear demarcation matters in hepatocellular carcinoma or colorectal liver metastasis confined to segment III, and in living donor or split-liver settings where preserving segment II perfusion and left hepatic venous drainage reduces ischemic congestion of the remnant. Educators can place this plate directly into hepatobiliary anatomy lectures on Couinaud segmentation, portal triad branching, and functional liver units, where students routinely confuse “left lobe” with left portal territories. Authors and clinicians may also use it in operative atlases, surgical consent materials, or multidisciplinary tumor board slides to communicate why a lesion in segment III calls for a limited resection versus a left hepatectomy. Anatomical accuracy verified by SciePro's Medical Advisory Board.