BACKGROUND: Laparoscopic liver resection (LLR) is a surgical procedure with varying degrees of difficulty depending on tumor status and surgical technique. Therefore, we aimed to evaluate the relationship between surgical difficulty levels and outcomes of LLR, particularly portal vein thrombosis (PVT). METHODS: We performed LLRs in 214 patients between January 2009 and December 2022. Among them, 200 patients who underwent pure LLR were allocated into three groups according to the Institut Mutualiste Montsouris (IMM) classification: Group I (n = 152), Group II (n = 26), and Group III (n = 22). The perioperative outcomes were also compared
risk factors for postoperative complications were evaluated. RESULTS: The operation time was significantly longer (p <
0.001) and intraoperative blood loss was significantly higher (p <
0.001) in Group III than in Groups I and II. The rates of complications of Clavien-Dindo (CD) grade 2 or higher (19.1% vs. 34.6% vs. 63.6%, p <
0.001) and CD grade 3 or higher (5.3% vs. 11.5% vs. 22.7%, p = 0.015) were significantly higher and postoperative hospital stay (9 vs. 13 vs. 16 days, p <
0.001) was significantly longer in Group III than in Groups I and II. The IMM classification (odds ratio [OR], 5.727
95% confidence interval [CI], 1.863-17.610
p = 0.002] and blood transfusion (OR, 6.410
95% CI, 2.215-18.549
p <
0.001) were independent risk factors for CD grade 2 or higher complication using multivariate analysis. PVT was the most common complication in patients with CD of grade 2 or higher, occurring in 14 of 48 patients. Hepatitis viral status (OR: 7.552, p = 0.021 [non-B non-C for HCV]) and the IMM classification (OR: 58.767, p <
0.001[II vs. I]
OR: 40.535, p = 0.002 [III vs. I]) were independent risk factors for PVT using multivariate analysis. CONCLUSIONS: The IMM classification could strongly predict postoperative complications, particularly PVT.