Definition and Classification of Minimally Invasive Major Hepatectomy (MIMH): A Literature Review and Expert Survey in the Fifth World Congress of the International Laparoscopic Liver Surgery (ILLS)

Objective: To explore the definition of minimally invasive major hepatectomy (MIMH) through an international expert survey and to establish a difficulty-based classification. Background: The definition of MIMH remains heterogeneous. While the classical definition (≥3 segments) has been widely accepted, technically demanding procedures such as right anterior sectionectomy (RAS) and right posterior sectionectomy (RPS) are increasingly regarded as “technically major,” yet consensus is lacking. Methods: A systematic review (2011–2024) identified 61 articles defining MIMH. Based on these findings, a web-based survey was distributed to 185 international liver surgeons between January and April 2025. The questionnaire evaluated expert opinions on the MIMH definition and the subjective difficulty of various laparoscopic anatomic resections (score 1–10). Results: A total of 112 surgeons responded (65% response rate). Most (89.3%) agreed that MIMH should include technically major resections, while 10.7% supported the classical definition alone. Among respondents who supported the inclusion of technically major hepatectomy, 80.0% specified RAS and RPS as technically major. Surgeons from large-volume centers (>75 minimally invasive hepatectomies per year) showed the strongest agreement (96.9%) and 93.5% identifying RAS/RPS as technically major. Subjective difficulty scores ranged from 3 for left hepatectomy to 7 for RAS, extended RPS, and central bisectionectomies, with others scoring 5–6. Conclusions: The international survey demonstrates a strong expert consensus for redefining MIMH to include technically major resections, specifically RAS and RPS. These findings provide a necessary foundation for future consensus updates and difficulty-informed clinical guidelines across minimally invasive liver surgery.