Revisiting the Institut Mutualiste Montsouris Difficulty Classification of Laparoscopic Liver Resection with the Data from a Personal Series—Evaluations for the Difficulty of Left Medial Sectionectomy and Length of Hospital Stay

The IMM (Institut Mutualiste Montsouris) difficulty classification for laparoscopic liver resection is based only on the type of surgical procedure. It is useful for assessing outcomes and setting benchmarks in a group sharing the same indications. There is, however, no left medial sectionectomy in the system. Its difficulty was evaluated using the same methodology as IMM with the data from a personal series. Furthermore, length of hospital stay was evaluated as the representative of short-term outcomes. IMM scores of our right and left hemihepatectomies, right anterior sectionectomy, and segment 7 or 8 segmentectomies are 3. That of left medial sectionectomies is 2, the same as right posterior sectionectomy and segment or less anatomical resections. Those of left lateral sectionectomy and partial resection are 0. The group with a score of 3 was divided into two groups—with and without extended hospital stays (extended only for right hemihepatectomies and right anterior sectionectomies). The difficulty of medial sectionectomy was positioned at the same level as posterior sectionectomy and segment or less anatomical resections. The result from the second evaluation may indicate that there are other factors with an impact on difficulty related to short-term outcomes, other than intraoperative surgical difficulty from the procedure itself.