A new look on liver anatomy: Needs and means to go beyond the Couinaud scheme
Authors: Henri Bismuth
Journal: Journal of Hepatology (2013)

Anatomy of the liver: An outline with three levels of complexity – A further step towards tailored territorial liver resectionsJournal of HepatologyVol. 60Issue 3PreviewThe vascular anatomy of the liver can be described at three different levels of complexity according to the use that the description has to serve. The first – conventional – level corresponds to the traditional 8-segments scheme of Couinaud and serves as a common language between clinicians from different specialties to describe the location of focal hepatic lesions. The second – surgical – level, to be applied to anatomical liver resections and transplantations, takes into account the real branching of the major portal pedicles and of the hepatic veins. Full-Text PDF Open Access The paper by Majno et al. [[1]Majno P. Mentha G. Toso C. Morel P. Peitgen H.O. Fasel J.H.D. Anatomy of the liver: an outline with three levels of complexity. A further step towards tailored territorial liver resections.J Hepatol. 2014; 60: 654-662Abstract Full Text Full Text PDF PubMed Scopus (67) Google Scholar], in this issue of the journal, makes the interesting proposal that we should retain the Couinaud's division of the liver into 8 segments but that we should be ready to break free from it when, as radiologists and surgeons, we perform the complex procedures that the modern treatment of surgical liver diseases requires. Claude Couinaud, a late colleague and friend, wrote an almost illegible book detailing the anatomy of the liver and its variations [[2]Couinaud C. Le foie, études anatomiques et chirurgicales. Masson, Paris1957Google Scholar]. Hidden in this book, there was the overarching conclusion that in most cases one could extract a simplified general pattern, in which 8 portal segments could be recognized (for the working summary of this representation, see the paper of Majno et al. in this issue, and a recent proposal for modification) [1Majno P. Mentha G. Toso C. Morel P. Peitgen H.O. Fasel J.H.D. Anatomy of the liver: an outline with three levels of complexity. A further step towards tailored territorial liver resections.J Hepatol. 2014; 60: 654-662Abstract Full Text Full Text PDF PubMed Scopus (67) Google Scholar, 3Bismuth H. Revisiting liver anatomy and terminology of hepatectomies.Ann Surg. 2013; 257: 383-386Crossref PubMed Scopus (70) Google Scholar]. Couinaud's system was popularized by two articles that I wrote in the early '80s, at the dawn of modern liver surgery, offering a more accessible description of Couinaud's work, and showing that liver surgery could and should be practiced having the segmental units in mind [4Bismuth H. Surgical anatomy and anatomical surgery of the liver.World J Surg. 1982; 6: 3-9Crossref PubMed Scopus (646) Google Scholar, 5Bismuth H. Houssin D. Castaing D. Major and minor segmentectomies "réglées" in liver surgery.World J Surg. 1982; 6: 10-24Crossref PubMed Scopus (191) Google Scholar]. In the article I stressed that the main landmarks were the three hepatic veins and the portal bifurcation. Axial imaging such as CT and MRI has lent itself beautifully to the use of Couinaud's coordinates, because the three hepatic veins and the portal bifurcation are so easy to recognise. Focal lesions can be described according to this system regardless whether the portal branches beyond the portal bifurcation follow it or not. But does modern liver surgery fit to the Couinaud's scheme? Majno et al. based on the literature and their experience as surgeons and anatomists (the readers are encouraged to study in detail the additional material) show that it does not [[1]Majno P. Mentha G. Toso C. Morel P. Peitgen H.O. Fasel J.H.D. Anatomy of the liver: an outline with three levels of complexity. A further step towards tailored territorial liver resections.J Hepatol. 2014; 60: 654-662Abstract Full Text Full Text PDF PubMed Scopus (67) Google Scholar]. This may mean practicing the principles of segmental surgery on smaller units than Couinaud's 8 segments (on units that we could call subsegments), but also on larger units corresponding to branches that do not follow the pattern of Couinaud, hence their more neutral denomination of "tailored territorial liver resections", implying that these units do not need to be systematised, only recognised and respected. I agree with this concept. Modern liver surgery has changed and has become a speciality in its own [[6]Bismuth H. Surgical specialization.Br J Surg. 2013; 100Crossref Scopus (4) Google Scholar]. It is only appropriate that its fundaments are questioned, and Majno et al. show that this is now at the same time possible and needed [[1]Majno P. Mentha G. Toso C. Morel P. Peitgen H.O. Fasel J.H.D. Anatomy of the liver: an outline with three levels of complexity. A further step towards tailored territorial liver resections.J Hepatol. 2014; 60: 654-662Abstract Full Text Full Text PDF PubMed Scopus (67) Google Scholar]. It is possible because radiological viewer programmes are more powerful and better. But I would also draw attention on the fact that, as the authors underscore with the word "empowerment", imaging studies have quit the old negatoscopes and the newer consoles of radiologists to enter the surgeon's laptops. This is an epistemological revolution in my view: liver imaging has left the physical space of the radiology department, or the hospital, to float in the "technosphere" where information can be more easily read, exchanged and discussed, from the office or from home. The immediacy by which high-quality imaging can be studied and shared is probably instrumental to the leap in surgical complexity that some of my colleagues are negotiating (illustrated in the additional material). Easy access means easy training and easy rehearsing, and facilitates the tenacious practice and preparation that make the most complex procedures possible. Why is this leap in complexity needed? Because specialized hepatobiliary surgeons now operate on more advanced disease, with more frequent reoperations on more fragile patients, and are under the constant pressure of minimizing complications and of sparing as much liver tissue as possible. Surgery based on the real vasculo-biliary anatomy is the only way to achieve these goals, and I am not surprised that it is becoming more customised. The call to free the operation from Couinaud's 8 segment scheme is in fact not subversive, it is the natural evolution of the concept we introduced in 1982 to the new imaging and surgical techniques, and to the identification of patients who can benefit from it. Of note, the articles I wrote in 1982 were before CT imaging, and the surgeon had to rely on preoperative and intraoperative ultrasound that by definition was done on the individual patient. There was no discrepancy to worry about. What about the third level, of the anatomy for the anatomist? The statement that 2nd-order branches are more numerous than in the traditional anatomical representations is obviously true. The observation that, historically, anatomists have tried to systematise the liver vascular architecture by adapting reality to concepts is also true, and that the different representations are in fact not incompatible with each other is interesting and plausible. While considering it still work in progress, I am sensitive to its appeal, and to the beautiful images that support it. I also like that this representation is less compelling than most, and that it draws the surgeon on a new ground, where there is greater freedom to plan and adapt the resections to the individual anatomy and to the individual disease. I always taught to my pupils that they should look for what makes their patient's condition special. I am glad that it has been understood. Couinaud introduced his book by quoting: "The human race wants simple ideas. But reality is complicated" (Julien Benda). The question is: where the needle stops going from the simple to the complicated. I would say: it depends on the needs. The authors declared that he does not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.