Validation of the IMM classification in laparoscopic repeat liver resections for colorectal liver metastases

Background: To validate the Institut Mutualiste Montsouris classification as a difficulty scoring system applicable to laparoscopic repeat liver resections and identify risk-factors of unexpected difficulty. Methods: From a prospectively collected database between 2000 and 2019, patients undergoing laparoscopic repeat liver resections were classified according to the Institut Mutualiste Montsouris classification. Doubly robust estimators (weighted regressions) were used to assess the effect of factors on intraand postoperative outcomes and allowed for strong adjustment on age, body mass index, American Society of Anesthesiologists, carcinoembryonic antigen, number, and size of lesions. Unexpected difficulty was defined as a composite indicator which included substantial blood loss and/or substantial operative time and/or conversion. Results: Of 205 laparoscopic repeat liver resections patients, 87, 25, and 93 procedures were classified as grade 1, 2, and 3 laparoscopic repeat liver resections, respectively. After doubly robust adjustment, the IMM classification was associated with blood loss (Cohen f(2) 0.12; P = 0.001), operative time (Cohen f(2) 0.07; P = .001), and length of stay (Cohen f(2) 0.13; P = .001), as well as with the risk of both minor and severe complications (odd ratio = 2.94; 95% confidence interval: 2.06-4.20) and the chances of achieving textbook outcome (relative risk = 0.57; 95% confidence interval: 0.41-0.81). Independently from the Institut Mutualiste Montsouris classification, a first major hepatectomy (relative risk = 1.15, 95% confidence interval: 1.03-1.29) as well as sinusoidal obstruction syndrome (relative risk = 1.24, 95% confidence interval: 1.09-1.41) were independent risk factors of unexpected difficulty. A first major resection was associated with decreased chances of textbook outcome (relative risk = 0.53; 95% confidence interval: 0.33-0.85). Conclusion: The Institut Mutualiste Montsouris classification is a valuable difficulty scoring system for laparoscopic repeat liver resections procedures, while previous major resection and presence of sinusoidal obstruction syndrome are likely to jeopardize the outcomes. (c) 2021 Elsevier Inc. All rights reserved.