How I do it: the technique of intraoperative ultrasound of the liver using the ligamentum venosum as the landmark

Introduction
Liver surgery planning relies on preoperative cross-sectional imaging, intraoperative assessment, and intraoperative ultrasound (IOUS) examination. Although palpation and visual inspection can identify large/superficial tumors, such strategies can miss the location of small deep tumors or assess their proximity to crucial structures. IOUS has been used for decades and remains the most sensitive modality for detecting the tumor location, size, and relationship to inflow/outflow and for assessing resectability [1]. In addition, IOUS facilitates parenchymal-sparing hepatectomies, fluorescence-guided surgery, and intraoperative ablation. Therefore, mastery of IOUS is essential for liver surgeons, as IOUS directly influences the accuracy of surgical decision-making and the safety of liver resection [2].