Page 44 - Read Online

Page 2 of 6 Russolillo et al. Mini-invasive Surg 2023;7:3 https://dx.doi.org/10.20517/2574-1225.2022.74

INTRODUCTION
Liver surgery has changed profoundly over time. Minimally-invasive approaches are spreading; the renewed
enthusiasm for the study, diffusion, and application of anatomical liver studies have driven two significant
revolutions that contributed to this evolution.

Two international and one European consensus conference recognized laparoscopic liver resection (LLR) as
safer and more advantageous than open surgery regarding morbidity, blood loss, and length of hospital
[1-3]
stay .

Several radiological studies and surgical strategies confirmed that the anatomy of the liver is more complex
than what Couinad described. Takasaki et al. described “cone units” as the smallest anatomical parts of the
[4]
liver supplied by a tertiary branch with bases on the liver surface and peaks toward the hilum . Majno et al.
reported a median number of 20 (range 9-44) of second-order branches given off by the left and right portal
[5]
veins . Based on these contributions, the Tokyo 2020 Expert Consensus Meeting described the presence of
one to several tertiary pedicles in each segment . They defined subsegmentectomy as a parenchymal
[6]
resection within a portal segment inferior to the entire segment of Couinaud.

Because of these revolutions, modern liver surgery encompasses a wide range of LLRs based on the actual
vascular-biliary anatomy that ranges from minor anatomical resections (ARs) to complex non-anatomical
resections (non-ARs).

According to the anatomic variations of the secondary and tertiary branches of the hepatic veins and the
portal pedicles and the absence of extrahepatic landmarks for these smaller liver units, intraoperative
ultrasound (IOUS) became an indispensable tool to understand the actual anatomy and plan a tailored LLR.

[7-8]
The four-step method (the “4 C's”) is a valuable technique based on IOUS ability (rules 1 and 2) and
resection counseling IOUS role (rules 3 and 4).

1. Compose the three-dimensional mind map. First, perform accurate ultrasound mapping of the
parenchyma, understanding connections between the target nodules and the surrounding vascular
structures.

2. Create the sketch. Deep vascular elements are brought back to the Glissonian of the liver surface using
cautery to make a drawing. The aim is to guide the surgeon and help them recall the liver anatomy map
relative to the target. Following the sketch, resection lines are marked on the Glissonian sheaf to bring the
structures to the surface to be sectioned and preserved.

3. Heck the way. Only the deeper structures are shown on the map sketch as a Glissonian projection. For
this reason, controlling the section plane while proceeding with resection by IOUS is helpful. The resection
line can be easily visualized as an inhomogeneous hyperechoic artificial line in the parenchyma. Using this
landmark, the surgeon can check the resection plane as needed during transection to respect the vascular
structure margins.