Learning process of laparoscopic liver resection and postoperative outcomes: chronological analysis of single-center 15-years’ experience

Background Limited studies have reported the actual learning process of laparoscopic liver resection (LLR). This study aimed to chronologically evaluate our 15 years’ experience of LLR. Methods All consecutive LLRs between 2006 to 2020 were retrospectively analyzed. The time period was divided into three groups; first (2006–2010), second (2011–2015), and third (2016–2020) period. The primary endpoint of this study was a composite of overall (Clavien–Dindo grade ≥ II) or major (grade ≥ IIIa) postoperative complications within 30 days. Using the IWATE criteria (four difficulty levels based on six indices), LLR was categorized as basic (