Background The Brisbane 2000 Terminology for Liver Anatomy and Resections, based on Couinaud’s segments, did not address how to identify segmental borders and anatomic territories of less than one segment. Smaller anatomic resections including segmentectomies and subsegmentectomies, have not been well defined. The advent of minimally invasive liver resection has enhanced the possibilities of more precise resection due to a magnified view and reduced bleeding, and minimally invasive anatomic liver resection (MIALR) is becoming popular gradually. Therefore, there is a need for updating the Brisbane 2000 system, including anatomic segmentectomy or less. An online "Expert Consensus Meeting: Precision Anatomy for Minimally Invasive HBP Surgery (PAM‐HBP Surgery Consensus)" was hosted on February 23, 2021. Methods The Steering Committee invited 34 international experts from around the world. The Expert Committee (EC) selected 12 questions and two future research topics in the terminology session. The EC created seven tentative definitions and five recommendations based on the experts’ opinions and the literature review performed by the Research Committee. Two Delphi Rounds finalized those definitions and recommendations. Results This paper presents seven definitions and five recommendations regarding anatomic segmentectomy or less. In addition, two future research topics are discussed. Conclusions The PAM‐HBP Surgery Consensus has presented the Tokyo 2020 Terminology for Liver Anatomy and Resections. The terminology has added definitions of liver anatomy and resections that were not defined in the Brisbane 2000 system.

Laennec's capsule is a proper membrane of the liver, first described by Réné T. H. Laennec in 1802, covering not only the entire surface of the liver but also the intrahepatic parenchyma surrounding the Glissonean pedicles and the hepatic veins (HVs). It is an essential structure for establishing liver resection, especially anatomic liver resection, which involves the isolation of the extrahepatic Glissonean pedicles and the exposure of the main HVs. Regarding the location of the capsule, Laennec and Couinaud described it as adjacent to the confluence of the main HVs. Whereas, Hayashi revealed it to be around the peripheral branches. Recently, Kiguchi first reported that Laennec's capsule consists of two layers and proposed novel surgical procedures using this concept. Yet, its existence is still debated. Herein, we show the precise anatomy and histology of Laennec's capsule around the HVs including its twolayered composition: one derived from the pericardium (the cardiac Laennec's capsule) and the other from the proper membrane (the hepatic Laennec's capsule). Using these findings, we demonstrate three surgical approaches to the main HVs and emphasize the significance of the craniocaudal parenchymal dissection especially for laparoscopic anatomic liver resection.

In this systematic review, we aimed to clarify the useful anatomic structures and assess available surgical techniques and strategies required to safely perform minimally invasive anatomic liver resection (MIALR), with a particular focus on the hepatic veins (HVs). Methods: A systematic review was conducted using MEDLINE/PubMed for English articles and Ichushi databases for Japanese articles through September 2020. The quality assessment of the articles was performed in accordance with the Scottish Intercollegiate Guidelines Network (SIGN). Results: A total of 3372 studies were obtained, and 59 were selected and reviewed.Due to the limited number of published comparative studies and case series, the degree of evidence from our review was low. Thirty-two articles examined the anatomic landmarks and crucial structures for approaching HVs. Regarding the direction

Background The concept of minimally invasive anatomic liver resection (MIALR) is gaining popularity. However, specific technical skills need to be acquired to safely perform MIALR. The “Expert Consensus Meeting: Precision Anatomy for Minimally Invasive HBP Surgery (PAM‐HBP Surgery Consensus)” was developed as a special program during the 32nd meeting of the Japanese Society of Hepato‐Biliary‐Pancreatic Surgery (JSHBPS). Methods Thirty‐four international experts gathered online for the consensus. A Research Committee performed a comprehensive literature review, classifying studies according to the Scottish Intercollegiate Guidelines Network method. Based on the literature review and experts’ opinions, tentative recommendations were drafted and circulated among experts using online Delphi Rounds. Finally, formulated recommendations were presented online in the Expert Consensus Meeting of the JSHBPS on February 23rd, 2021. The final recommendations were validated and finalized by the 2nd Delphi Round in May 2021. Results Seven clinical questions were selected, and 22 recommendations were formulated. All recommendations reached more than 85% consensus among experts at the final Delphi Round. Conclusions The Expert Consensus Meeting for safely performing MIALR has presented a set of clinical guidelines based on available literature and experts’ opinions. We expect these guidelines to have a favorable effect on the safe implementation and development of MIALR.

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