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Page 6 of 11 Sawa et al. Mini-invasive Surg 2024;8:30 https://dx.doi.org/10.20517/2574-1225.2024.43

Table 2. Surgical and postoperative outcomes between OLR and MISLR groups
OLR N = 781 MISLR N = 172 P-value
Liver resection complexity classification, n (%) < 0.001
Grade I 224 (28.7) 105 (61.0)
Grade II 172 (22.0) 47 (27.3)
Grade III 385 (49.3) 20 (11.6)
Conversion to open approach, n (%) - 7 (4.1) -
Use of inflow occlusion, n (%) 732 (93.7) 100 (58.1) < 0.001
Duration of inflow occlusion, median (IQR), min * 56 (40-76) 60 (40-90) 0.179
Blood transfusion, n (%) 113 (14.5) 3 (1.7) < 0.001
Surgical margin status, positive, n (%) † 124 (16.2) 14 (8.2) 0.008
Complication, n (%)
Bile leakage 59 (7.6) 4 (2.3) 0.012
Hepatic insufficiency 1 (0.1) 0 (0) > 0.999
Pulmonary complication 74 (9.5) 2 (1.2) < 0.001
SSI 32 (4.1) 1 (0.6) 0.022
90-day mortality, n (%) 2 (0.3) 0(0) -

* †
Assessed with 732 patients in OLR and 100 patients in MISLR group undergoing inflow occlusion. Data missing on surgical margin status,
positive for 15 patients in OLR group, and two patients in MIS group. OLR: Open liver resection; MISLR: minimally invasive liver resection; IQR:
interquartile range; SSI: surgical site infection.

Comparison of the surgical and postoperative outcomes between the OLR and MISLR groups
according to the complexity grade
The surgical and postoperative outcomes were compared between the OLR and MISLR groups according to
patients undergoing grade I resection [Figure 3], grade II resection [Figure 4], or grade III resection
[Figure 5]. The operative time in patients undergoing grade I, II, and III resections was similar between the
OLR and MISLR groups [Figures 3A, 4A, and 5A]. However, the blood loss, complication rate, and length
of hospital stay were significantly lower in patients undergoing grade I-III procedures in the MISLR group
than in the OLR group (all P < 0.05) [Figures 3-5].

DISCUSSION
Our group has gradually expanded the indications for MISLR over ten years to include low-complexity liver
resections and intermediate/high-complexity liver resections. This may enhance the safety of patients
undergoing MISLR. The estimated blood loss and complication rate were lower and hospital stay was
shorter in the MISLR group than in the OLR group in patients undergoing grade I-III resection
[Figures 3-5].

Our data suggest that careful patient selection for a minimally invasive approach and gradual expansion of
indications for MISLR to technically demanding procedures may lower the postoperative complication rate
and shorten the hospital stay in patients undergoing grade II (intermediate complexity) and grade III (high
complexity) liver resection. In the OLR group, the rate of CD grade ≥ II complications demonstrated an
increasing trend as the surgical complexity increased [Supplementary Figure 3]. However, in the MISLR
group, the rate of CD grade ≥ II complications was similar and approximately 10% in patients undergoing
grade I, II, and III resections [Supplementary Figure 4]. As a European multi-institution study suggested, a
[16]
long implementation process is necessary to allow for standardization and implementation to mastery .