Classification Of Hepatic Portal Vein In Central Region Based On Modern Visualization Technique And Its Application In Hepatectomy

Background:Anatomic liver resection(ALR)is currently the most effective treatment modality for primary and secondary malignancies of the liver.Accurate performance of anatomic liver resection requires detailed preoperative knowledge of the intrahepatic portal vascular anatomy,accurate segmentation of the liver,precise location of the lesion,and thorough surgical planning.Also,knowledge of the anatomy and variation of the landmark hepatic veins on the boundaries of the liver segments is of great value for anatomical hepatectomy.The anatomical location of the central hepatic region is unique,and understanding the vascular variation in the central hepatic region is important for the precise performance of radical hilar cholangiocarcinoma,radical gallbladder cancer,anatomical hemihepatectomy,and anatomical hepatic segment/subsegmental resection.However,the portal vein branching pattern in the central hepatic region is variable,the segmentation of the liver does not exactly follow the traditional Couinaud segmentation that is currently widely used in teaching and clinical practice,and there is some degree of variation in the relationship between the boundaries of the liver segment and the anatomical location of the landmark hepatic vein.Therefore,further study of the anatomy of the central hepatic region is warranted.Part Ⅰ.Classification of hepatic portal vein in central region based on modern visualization technology Objective:To study the anatomical structure and branching pattern of the portal vein in the central hepatic region and to perform 3D typing of the branching pattern of the portal vein in the central hepatic region.Methods:Based on the patient’s abdominal computed tomography(CT)data,a 3D visualization model of the liver and intrahepatic portal veins and hepatic veins was reconstructed using 3D visualization software.The branching pattern,origin and number of portal veins in the central region of the liver were observed and analyzed and 3D typing was performed.Results:1.The branching pattern of the portal sector veins of the liver could be divided into 6 types,among which type I was the most common with 166 cases(76.5%),type II with 25 cases(11.52%),type III with 12 cases(5.53%),type IV with 2 cases(0.92%),type V with 3 cases(1.38%),and type I + IV with 9 cases(4.15%).2.There were 3 types of sources of portal vein branches in the right anterior lobe of the liver: 191 cases(88.02%)of type I,17 cases(7.83%)of type II,including 6cases(2.76%)of type IIa,11 cases(5.07%)of type IIb,and 9 cases(4.15%)of type III.3.There were four branching patterns of the portal vein in the right anterior lobe of the liver: 105 cases(48.39%)of the cranio-caudal type,67 cases(30.88%)of the ventro-dorsal type,18 cases(8.29%)of the trifurcation type,and 27 cases(12.44%)of the quadrufurcation type.4.The portal branching pattern of P4 can be divided into 2 types,102 cases(47%)of type I and 115 cases(53%)of type II.P4 a is divided into 2 types and has several subtypes according to its portal branching origin,17 cases(7.83%)of type Ia,29 cases(13.36%)of type Ib,25 cases(11.52%)of type Ic,5 cases(2.3%)of type Id,5 cases of type Ib and 5 cases of type Ic.2.3%),21 cases of type Ⅰb + type Ⅰc(9.68%),2 cases of type Ⅰb + type Ⅰd(0.92%),3 cases of type Ⅰc + type Ⅰd(1.38%),65 cases of type Ⅱa(29.95%),43 cases of type Ⅱb(19.82%),4 cases of type Ⅱc(1.84%),and 3 cases of type Ⅱb + type Ⅱc(1.38%).p4 b was similarly divided into 2 types with several subtypes,type Ia had 66 cases(30.41%),type Ib had31 cases(14.29%),type Ic had 2 cases(0.92),type Ib+Ic had 3 cases(1.38%),type IIa had 107 cases(49.31%),type IIb had 5 cases(2.3%);type IIc had 3 cases(1.38%).Conclusions:The portal vein anatomy in the central region of the liver is complex and variable,and the portal vein branches in the right anterior lobe of the liver mainly originate from the right anterior branch,followed by the right branch trunk,and a small proportion from the left branch of the portal vein.The right anterior lobe portal vein branching pattern was the most common type with Couinaud fractionation,followed by Cho fractionation,and trifurcation and quadrufurcation types were rare.The complexity of the anatomy of the portal vein in the left medial lobe of the liver is mainly due to the multiple possible combinations of its origin.Part Ⅱ.Study of hepatic segment boundaries in the central region of the liver based on the portal perfusion territory Objective:Individualized liver segmentation was performed according to the branching pattern of the portal vein to observe the anatomy of the hepatic venous system around the liver segments and its role in segmental boundary delineation.Methods:Based on the 3D visualization model of the liver and intrahepatic vessels completed in Part I,individualized liver segment delineation was performed on the liver using 3D visualization software for portal venous perfusion territory analysis.The anatomical structure of the hepatic venous system was observed and typed.By virtual hepatectomy based on portal vein basin analysis,the middle hepatic vein(MHV),umbilical fissure vein(UFV)and anterior fissure vein(AFV)were observed to be revealed on the virtual hepatectomy section.Results:1.Based on the portal vein branching situation to calculate the portal perfusion territory,the individualized liver segment division of the liver can clearly show the boundary of each liver segment on the liver surface,and the anatomical situation of the liver segment boundary within the liver parenchyma and the anatomical relationship between the hepatic vein and the liver segment boundary can be clearly observed by virtual hepatectomy and adjusting the transparency of the liver parenchyma.2.MHV can be divided into the following 3 types according to its branching pattern: 143 cases(65.9%)of type I,64 cases(29.49%)of type II,and 10 cases(4.61%)of type III.After performing virtual left hemicolectomy,MHV was completely revealed on the liver section in 174 cases(80.18%)and partially revealed in 43 cases(19.82%).3.the presence of UFV was observed in 197 patients(90.78%).the UFV was classified into 3 types,type I in 35 cases(17.77%),type II in 25 cases(12.69%)and type III in 137 cases(69.54%).After virtual left hepatic lobectomy,UFV was observed in 168 cases(77.42%)on liver sections.4.AFV was observed in 136(62.67%)patients.AFV can be classified into 4types,71(52.21%)in type I,7(5.15%)in type II,9(6.62%)in type III,47(34.56%)in type IV,and 2(1.47%)in type I + IV.AFV was observed on liver sections after virtual liver resection in 97 cases(44.7%).Conclusions:In a small number of patients,MHV does not always travel along the left and right hepatic hemispheric borders.UFV can be present in the vast majority of patients and can landmark hepatic veins between the left inner and left outer lobes.Compared to UFV,AFV has a lower probability of occurrence and its use as a landmark vein in the ventral(sub)segment and dorsal(sub)segment of the right anterior lobe of the liver is only applicable in a small number of patients.Part Ⅲ.Application of individualized liver segmentation based on modern visualization techniques in anatomical hepatectomy Objective:To investigate the application value of three-dimensional(3D)visualization technology in anatomical hepatectomy for individual liver segmentation and surgical planning.Methods:In this study,65 patients with hepatocellular carcinoma who underwent laparoscopic anatomical hepatectomy were retrospectively collected and analyzed.Among them,28 patients were treated with 3D visualization technology for 3D reconstruction and surgical planning before operation,and Indocyanine green(ICG)fluorescence staining was performed according to the 3D visualization results during operation(3D group),and no 3D visualization reconstruction was performed before operation.The traditional method was used to determine the extent of liver resection in 37 patients(traditional group).In the 3D group,a 3D visualization model of the liver,intrahepatic vessels and tumors was reconstructed based on the enhanced CT scan data of the patient before operation.According to the patient’s portal vein branch pattern,the individual liver segment was divided to determine the hepatic segment or subsegment where the tumor was located,and the tumor-bearing portal vein branches were accurately located.Virtual hepatectomy was performed for surgical planning and the expected liver volume was calculated.Intraoperative ICG fluorescence staining was used to identify the boundaries of tumor-bearing liver segments on the surface of the liver and within the liver parenchyma.In order to reduce the difficulty of portal vein puncture or anatomical occlusion of Glission pedicle,3D visualization technology was used to simulate intraoperative ultrasound images or plan portal vein approach.In the traditional group,no three-dimensional visualization reconstruction was performed before operation,and laparoscopic anatomical hepatectomy was performed according to the traditional method.The perioperative conditions such as intraoperative hepatic vein exposure,intraoperative blood loss,blood transfusion,postoperative complications and follow-up results were statistically analyzed.To investigate the effectiveness and feasibility of individualized liver segmentation and surgical planning based on three-dimensional visualization technology in laparoscopic anatomical hepatectomy.Results:1.In the 3D visualization model,the scope of each hepatic segment,the hepatic segment where the tumor was located,the perfusion range of the tumor-bearing portal vein,and the anatomical position relationship between the target hepatic segment and the surrounding hepatic veins were clearly displayed.2.Among the 28 patients in the 3D group,27 patients(96.4%)successfully completed liver segment staining.The staining range of the liver surface was highly similar to that of the tumor-bearing portal vein basin in the preoperative 3D visualization software.3.Compared with the conventional group,patients in the 3D group had a higher rate of anatomical hepatectomy,less intraoperative blood loss,and shorter postoperative hospital stay.Conclusions:The use of three-dimensional visualization technology for individualized liver segmentation and virtual hepatectomy is helpful to confirm the hepatic segment where the tumor is located,accurately locate the tumor-bearing portal vein,and understand the spatial relationship between the boundary of the target liver segment and the surrounding landmark hepatic veins.By simulating intraoperative ultrasound images and planning the approach of the target portal vein,it is helpful to guide the portal vein puncture and the anatomy of the Glission pedicle,which is helpful for the successful implementation of laparoscopic anatomical hepatectomy.Compared with traditional methods,the use of 3D visualization technology in planning laparoscopic anatomical hepatectomy is helpful to reduce intraoperative blood loss and shorten postoperative hospital stay.