Laparoscopic liver resection (LLR) has evolved and improved over the years with a corresponding expansion of its indications. In 2014, after the 2nd International Consensus Conference on LLR in Morioka, Japan, it was concluded that LLR can be the standard of care for minor resections and is in the exploration phase for major resections. With increasing evidence supporting its safety and benefits, along with the expansion of accepted indications, the popularity of LLR has grown with an exponential increase in the number of surgeons adopting LLR worldwide (1-6).
This has led to many surgeons in large centers around the world attempting more challenging cases as they grew in experience and case volume (7,8). This is despite the learning curve in LLR being significant as the complexity of various LLR procedures can be quite subjective and its difficulty often not well appreciated by surgeons early in their learning curve (4,9,10). With this rise in adoption of LLR by surgeons of variable experience and skill level around the world, there was a recognized need for a way stratify the difficulty that they may experience attempting LLR in their center, scoring systems in surgery are not new and can be useful in this context. If designed and developed well, it can serve as an objective way to guide decision making and case selection (11,12). It was therefore not surprising that the concept of a difficulty score in LLR was a hotly discussed topic in the last consensus meeting as well as in recent inaugural World Congress of International Laparoscopic Liver Society in Paris (2,13,14).
We read with great interest the study by Kawaguchi et al. titled: “Difficulty of Laparoscopic Liver Resection: Proposal for a New Classification”, recently published in Annals of Surgery. They analyzed their extensive experience of 452 LLR over a 20-year period and proposed a new classification of LLR difficulty. They utilized three intra-operative parameters as surrogates of difficulty, namely, blood loss, operative time and conversion rate and used their measures of central tendency such as median values or overall rates as threshold for assigning the points. These points then grouped various LLR procedures into three groups (low, intermediate and high grades of difficulty) (Tables 1,2). After the grouping, they further reported that the post-operative outcomes such as overall morbidity and major complications correlated significantly with increasing groups of difficulty (15).
Based on the study population and outcome analysis of Kawaguchi et al., they allocated 1 point for each factor (blood loss >100 mL; operative time >190 min; conversion rate >4.2%) and classified different LLR procedure into three groups based on the number of points each LLR procedure had (Table 1). They recommended that the group I procedures are less difficult and can be attempted by liver surgeons at the beginning LLR phase and group III procedures should only be performed by experts. This study provides valuable insight and evidence that further acknowledges that the challenges of LLR cannot be extrapolated from open approaches. It provides an easy-to-use guide of which LLR procedures are easier and which ones are more technically demanding. This is unique and objective as it is created from intra-operative data on the basis of common and well-established surrogates of technical difficulty such as blood loss, operative time and conversion rate. It was further internally validated with their postoperative outcomes. However, as the authors rightly pointed out, this study was limited by retrospective data from a single institution study by a single surgeon, albeit by a renowned institution lead by with an eminent expert and pioneer in LLR (Brice Gayet). It is also because this score is generated by a single group of expert surgeons, the arbitrary thresholds derived from their experience which provided the points (blood loss >100 mL; operative time >190 min; conversion rate >4.2%) may not hold true for the rest of the world, especially in centers or surgeons with less experience. Consequently, the difficulty score based on this expert group may be an under-estimation or an under-representation of the current reality in other centers.
Furthermore, some information was not available in the study including the proportion of patients with significant chronic liver disease such as cirrhosis or chemotherapy associated steatohepatitis. Not unsurprisingly, the majority of the indications were for colorectal liver metastases (CRLM) and hepatocellular carcinoma (HCC) accounted for less than 10% of their study population, consistent with the disease pattern common in the West. This differs from most centers in the East where patients with HCC on the background of cirrhosis account for a large proportion (4,16). This study and its findings are therefore likely more applicable to centers with similar disease pattern with CLRM as its major indication for liver resection. The classification may be less translatable to other regions of the world or centers which has a larger portion of cirrhotic and HCC patients.
If we were to solely consider complexity, traditional nomenclature such as the Brisbane classification in terms or what defines a major or minor resection in open liver surgery, are less applicable in LLR (17,18). Complexity or difficulty scores are not new in liver surgery, Lee et al. previously published a perceived complexity score for open liver resection based on a survey of 66 experts (11). Earlier, Ban et al. also published a difficultly score for LLR which has been validated by several groups since its introduction (19-23). The LLR difficulty score by Ban et al. was created by a group of Japanese LLR experts from multiple institutions based on factors that they deemed from their own subjective experience as factors that can potentially beget a LLR procedure less or more difficult (19,20). They identified five significant factors—the type of the planned LLR procedure, tumor location, presence of Child-Pugh B liver cirrhosis, tumor’s size (3 cm), location and its proximity to major vessels (main or second order Glissonian pedicles, major hepatic veins or inferior vena cava). The degree of difficulty was assessed by the operator using a score of 1–10 and the score is then similarly translated to 3 levels of difficulty (low, intermediate and high). Linear modeling was performed and there was good inter-rater agreement concordance between the operators’ and reviewers’ assessments of difficulty. The value of score of Ban et al. lies in that it utilizes available and common factors all liver surgeons assess pre-operatively during their surgical planning, thus it is familiar and routine. It is a score ranging from 1–10, providing a more gradual gradient and finer distinction between procedures of increasing difficulty. This may be useful as it allows surgeons early in their LLR learning curve to adopt a gentler slope to climb and also provide guidance on the proper and appropriate selection of cases according to their level. This score was published in 2014 and therefore had the benefit of time, which allowed several groups including our own center to externally validate it (3,21-23). This score was later modified by Wakabayashi et al. and named it as the IWATE criteria by these additional refinements such as including segment 1, distinguishing segment 4 into S4a and S4b, adding hand-assisted/hybrid as another factor and having 4 levels based on 0–12 points [low (0–3), intermediate (4–6), advanced (7–9), expert(10–12)] (24). This IWATE score has yet to be validated.
Table 1 summarizes and compares the features of the two studies and their difficulty score. As illustrated, in Kawaguchi’s study, group I and II has only two procedures per group and group III has six procedures. Without experience or a mentor’s guidance, a beginner LLR surgeon may find it challenging to distinguish which of the six procedures in group III are more or less difficult. Some of the factors used in Ban’s study and the IWATE criteria can help in this aspect. For the same procedure, there are nuances that contribute to its difficulty. For example, a right hepatectomy in cirrhotic patient with a large tumor near the hilum is quite different from a right hepatectomy in a patient with a normal liver and a small tumor far away from hilum. Table 2 lists the procedures in the three groups in Kawaguchi’s study and compares it alongside Ban’s study, the IWATE criteria and Hasegawa’s study, illustrating some of their similarities as well as their unique features (15,16,19,24). Each of the difficulty scoring systems has its own pros and cons (25). An ideal scoring system should be simple, accurate, quantitative, widely applicable and well validated. Its assessment factors should be easily available pre-operatively as well. While Kawaguchi’s and Ban’s score each have their merits, and in their way have helped advance the concept of an objective assessment of LLR difficulty, the perfect difficulty score is probably still a work-in-progress (16). There exists other known patient and tumor factors that have shown to affect the difficulty of a LLR, but have not been evaluated and/or left out in these scores. In a recent survey by the European-African Hepato-Pancreato-Biliary Association (E-AHPBA), there were 26 factors in four categories such as patient history, surgical history, tumor factors and planned operation that were identified from the literature to be potential factors that could affect the difficulty of LLR. The respondents used a modified Visual Analogue Scale (0–5) to rate how much each of the 26 factors they felt affected the difficulty of a resection. Based on the majority of the surgeons surveyed, it reported that difficulty was likely to be significantly increased by the following factors: a BMI >35, neo-adjuvant chemotherapy, repeated liver resection(s) and concurrent procedures. These factors have not been included in the existing difficulty scoring systems (25). Hasegawa et al. also recently published their version of a LLR difficulty score, using operative time as a predictor of difficultly, other than the additional similar factors they found as predictors, such as extent of resection, tumor location, BMI (< or >30 kg/m2); platelet counts (< or > 100k) were also found as a significant factor in their score. These indicates that there may be some other factors that deserve a review, and may be considered to be incorporated in the design of a better and a more accurate score (16). These scores will benefit from larger multi-institutional studies from both Eastern and Western experience for external validation and further refinement of the ideal LLR difficulty score (16).
In summary, the study of Kawaguchi et al. has provided great insight from their breadth and depth of experience and has created a simple classification to guide surgeons on the difficulty of various LLR procedures. The perfect difficulty score is something we look forward to having one day. As with most things, it probably lies somewhere in between extremes: between one that is easy to use and one that is complex and rigorous enough to be accurate and applicable in most situations.
Conflicts of Interest: The authors have no conflicts of interest to declare.
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Cite this article as: Lee SY, Chiow KH, Goh BK, Chan CY. The challenge in determining difficulty of laparoscopic liver resection: are we there yet? Laparosc Surg 2018;2:23.