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IMM Difficulty Score

Laparoscopic Liver Resection Difficulty (Italian Multi-Model)
Scores the technical difficulty of laparoscopic liver resection across five domains. Guides patient selection and centre capability requirements for minimally invasive hepatectomy.
Liver Surgery Laparoscopic Hepatectomy Surgical Difficulty
IMM Score — 5 Domains
1. Tumour / Segment Location
2. Proximity to Major Vessels
3. Extent of Hepatectomy
4. Background Liver Disease
5. Previous Hepatectomy
0
IMM Score (0–9)
Low Difficulty
Suitable for trained laparoscopic surgeon

IMM Score Domains

DomainOptionsScore
Segment locationAnterolateral (S2, S3, S5, S6)0
Posterosuperior (S1, S4a, S7, S8)+2
Major vessel proximity>1 cm from hepatic vein/IVC0
Within 1 cm+2
Extent of hepatectomyMinor (<3 segments)0
Major (≥3 segments)+2
Background liverNormal0
Cirrhosis / fibrosis (F3–F4)+2
Previous hepatectomyNo0
Yes+1

Difficulty Classification

IMM ScoreDifficultySurgical Requirement
0–3LowTrained laparoscopic surgeon (Fellowship in MIS)
4–6ModerateExperienced laparoscopic hepatic surgeon (>60 LH cases)
7–9HighExpert hepatic laparoscopist or robotic approach

Comparison: IMM vs Other Difficulty Scores

  • IWATE score (Kawaguchi 2015): uses tumour size, location, proximity to vessels, performance status, and extent — validated in Japanese centres across 4 grades
  • IMM (Ciria 2017): validated in Italian multi-centre series; 5 domains, simpler structure than IWATE
  • Southampton score (Abu Hilal 2016): uses 3 grades based on procedure type — widely adopted in European consensus
  • No single difficulty score is universally adopted — institutions commonly use the one validated in their setting

Clinical Application

  • Posterosuperior segments (S1, S7, S8) are the most technically challenging — require expertise in parenchyma-sparing techniques and intraoperative ultrasound
  • Cirrhosis increases difficulty through reduced parenchymal compliance, friability, and risk of haemorrhage — also reduces safe remnant liver volume
  • Previous hepatectomy causes adhesions, altered anatomy, and reduced remnant function reserve — mandates volumetric assessment (FLR/TLV) before re-resection
  • ERAS for liver surgery: laparoscopic approach associated with less blood loss, shorter hospital stay, and similar R0 resection rates compared to open hepatectomy

References

  1. Ciria R, et al. A systematic review and meta-analysis comparing the short- and long-term outcomes for laparoscopic and open liver resections for hepatocellular carcinoma: updated results from the European Guidelines Meeting on laparoscopic liver surgery. Ann Surg Oncol. 2019;26(1):252–263.
  2. Kawaguchi Y, et al. Standardization of difficulty for laparoscopic hepatectomy: proposal for a difficulty scoring system (IWATE criteria). J Hepatobiliary Pancreat Sci. 2015;22(11):865–872.

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Southampton Difficulty Score BCLC Staging ALBI Score