As LC became more common, the frequency of VBI was expected to decrease; however, the incidence of VBI remained steady at 0.5% [2, 4]. One explanation for this discrepancy could be the existence of anatomical variations such as the anomalous bile duct. It is universally accepted that in all biliary systems, including the anomalous bile duct converging to the hilar plate system [1, 5, 6, 10], the risk of VBI can be decreased by avoiding dissection through the hilar plate. The concept of the CVS have been proposed to avoid misidentification of major vasculo-biliary components during LC . However, standardized landmark, approach or procedure for achieving CVS had not been advocated. Recently, Tokyo Guidelines 2018 described that LC should be performed above the imaged line between the base of segment IV of the liver and the roof of the Rouviére’s sulcus for safe LC . Similar referenced line proposed by Gupta et al. in 2019 , in which LC must be done ventral and cephalad to the line joining the roof of the Rouviére’s sulcus and base of segment 4 . We proposed the segment IV approach in 2019, which is based on the operative management for safe LC by dissecting the gallbladder first along the D-line, the right edge of the hilar plate system. D-line lies right side as compared with former two referenced line and the surgical gauze, which is placed along the D-line, plays a useful landmark for safe dissection of hepato-cystic triangle.
As have been described in our original report, the anterior Glissonean pedicle across on the back side of the D-line which is easily identified by using flexible laparoscope, and is secured by using of blunt-tip dissecting forceps. Also D-line lies apart more than 3mm from the roof of the Rouviére’s sulcus regardless of the shape of caudal surface of the segment IV .
The operating gauze, which is isolated along the D-line, acts as a constantly visible landmark to safe dissection. Based on our experience, the D-line corresponds to the narrow segment of the gallbladder neck, which facilitates the isolation of the gallbladder . While the D-line corresponds to proximal root of the cystic plate, bile ducts are not exist on the side of the D-line. Thus, the segment IV approach may be useful for avoiding VBI while performing LCs in patients with an ABD. In this study, the CVS was achieved in all cases without exposing the ABD. Intraoperative still pictures of the CVS indicated that the dissection proceeded to the right border of the hilar plate. The advantage of the segment IV approach is its simplicity. This approach only requires two steps to achieve the CVS: isolation of the gallbladder along the D-line and dissection of the cystic structure towards the D-line. The question will be the advantage of the D-line method as compared to conventional fundus-down cholecystectomy. Strasberg et al. reported that most VBI, especially in inflamed gallbladder, had been caused by fundus-down approach, due to the thickening and shrinking of the cystic plate . We consider the risk of fundus-down approach that lack of the landmark to which the gallbladder is to dissect. As long as the D-line is secured by surgical gauze, hepato-cystic triangle is dissected safely without misidentification. Once the gallbladder is isolated by surgical gauze, the CVS can be achieved by removing fat and fibrous tissue in front of the gauze. Thus, the segment IV approach enables a surgeon to achieve the CVS simply, regardless of the presence or absence of an ABD.
The segment IV approach has some limitations. The approach is not applicable in cases where the margin of the gallbladder cannot be recognized for anatomical identification of the D-line due to inflammatory adhesion with surrounding structures . Although we have not experienced such complications in the current study, which is better to convert to open surgery, since laparoscopic dissection of the gallbladder from the lateral side can lead to injury of vasculo-biliary components.
In conclusion, it is a promising technique, even in patients with an ABD.