Prevalence and clinical significance of the Sg6/Sg7 intersegmental veins based on re-evaluation of the Couinaud classification for the right posterior portal vein.

Although Segment 6(Sg6) and Segment 7(Sg7) are two independent units, there are currently no clear anatomical boundary markers between Sg6 and Sg7. This study aimed to identify intersegmental veins (ISV) in the intersegmental plane of Sg6 and Sg7, and evaluate the prevalence of ISV, and its clinical significance in anatomical hepatectomy. We analyzed data from 180 patients undergoing abdominal computed tomography (CT) examination, and simultaneously performed 3D reconstruction models of the liver for each patient. The right posterior portal vein was analyzed and re-typed. Furthermore, the existence of ISV was defined, and prevalence and confluence patterns of ISV were analyzed. The author attempted to apply ISV to laparoscopic S6/S7 segmentectomy. We sorted data from the right posterior portal vein and divided it into six types. The ISV could be identified in 82.2% (148/180) of the patients, which were derived from the right hepatic vein (RHV) (91.9%) and right posterior inferior vein (IRHV) (8.1%). Ten ISV-guided laparoscopic Sg6/Sg7 segmentectomy were successfully carried out, seven patients underwent Sg6 segmentectomy, and three patients underwent Sg7 segmentectomy. There was no perioperative mortality. The median operative time was 223 min (range 181-260 min). The median blood loss was 200 ml (range 150-310 ml). The R0 resection rate was 100%. The ISV may be a candidate vessel to distinguish the boundary of the right posterior sector; it is expected to be a landmark in the liver parenchyma of anatomical hepatectomy.