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Sawa et al. Mini-invasive Surg 2024;8:30 https://dx.doi.org/10.20517/2574-1225.2024.43 Page 5 of 11

Figure 2. (A) Annual number of LR cases by each complexity grade and (B) proportion of MISLR cases of each complexity grade in
2011-2017 and 2018-2023 Aug. MIS: Minimally invasive surgery; LapAssisted: laparoscopic assisted; Aug: August; LR: liver resection;
MISLR: minimally invasive liver resection.

2018, and the proportion of grade III (high-complexity) resections has risen since 2022 [Figure 2]. During
2011-2017, 24.4% of the MISLRs were grade II and III procedures, and this proportion increased to 44.1%
during 2018-2023.

Comparison of the surgical and postoperative outcomes between the OLR and MISLR groups
The proportion of liver resections according to complexity was significantly different between the OLR and
MISLR groups. The proportion of grade I and III procedures was the highest in the MISLR and OLR
groups, respectively [Table 2]. Bile leakage, pulmonary complications and surgical site infection were
significantly less in the MISLR group than in the OLR group [Table 2]. The operative time, blood loss,
complication rate, and length of hospital stay were significantly lower in the MISLR group than in the OLR
group [Supplementary Figure 2]. In the OLR group, the operative time, blood loss, complication rate, and
length of hospital stay increased significantly with higher surgical complexity (from grade I to III resection,
trend P < 0.001) [Supplementary Figure 3]. In the MISLR group, the operative time and blood loss increased
significantly as the surgical complexity rose (from grade I to grade III resection, trend P < 0.001)
[Supplementary Figure 4]. However, the complication rate and length of hospital stay were similar in the
MISLR group across all grades of surgical complexity [Supplementary Figure 4].