Lecture : Hialr cholangiocarcinoma is the adenocarcinoma arising from the hepatic duct confluence and this tumor was described for the first time in 1965 by Dr. Gerald Klatskin, so this tumor is also called Klatskin’s tumor. He suggested that this tumor is an unusual tumor with distinctive clinical and pathological features. In this paper, Dr. Klatskin suggested that palliative surgery aimed at relieving biliary obstruction may restore the aptients to a good state of health for a remarkably long period of time. Such palliation may be achieved by internal drainage of only one of the major intrahepatic bile ducts. However, reported prognostic factors of hilar cholangiocarcinoma are resectability itself and resection margin status, L/N metastasis status, neural plexus invasion, cellular differentiation and gross type. Among them, T stage associated resectability and resection margin status can be modified by a surgeon. Therefore, complete resection without residual tumor is primary goal of surgical therapy for hilar cholangiocarcinoma. If we think of mode of spread and infiltration of hilar cholangiocarcinoma, there are both vertical invasion and longitudinal infiltration. If you are looking at the anatomical relationship of ductal bifurcation and right hepatic artery and portal vein, vertical invasion occurs very easily to right hepatic artery and portal vein due to very close proximity of three structures within hepato-duodenal ligament. Occasionally, portal vein invasion and right trisectionectomy was required for pathologically curative resection. Another problem of mode of spread and infiltration is a longitudinal infiltration which means the longitudinal spread of the tumor along the bile duct distally and proximally, which prohibits R0 resection for hilar cholangiocarcnoma. According to Nimura group from Nagoya university, longitudinal extension of HC consists of mucosal or submucosal infiltration depending on the tumor growth pattern. Mucosal extension is predominaltly seen with papillary and nodular tumors, while submucosal extension is mainly seen with sclerosing tumors. The length of longitudinal extension is determined by the type of invasion, with a mean length of 10-20 mm for mucosal spread and 6-10 mm for submucosal spread. Therefore, to achieve negative microscopic resection margins more than 1 cm in the infiltrating type and more than 2 cm in the papillary type and nodular type is recommended. On the other hand, from the oncological point of view aiming at wider margins, P Neuhaus from Berlin insists that RTS is the most preferable approach to achieve R0 resection for hilar cholangiocarcinoma because the secondary branch of right duct are more likely to be involved earlier when the tumor arise at the biliary confluence. In general, type 4 HC is considered unresectable. However, according to detailed confluence pattern study of the bile duct branching of the medial segment, RTS can result in R0 resection for type 1, in which B4 join the left hepatic duct close to the hilar confluence. For some cases of type 2, in which B4 join the left hepatic duct far from the hilar confluence, we might achieve R0 resection if we understand anatomic right hepatic trisectionectomy very well. Moreover, the techniques of right trisectionectomy is relatively easy, With regards to the technique of right trisectionectomy of liver, Dr Starzl described the techniques in detail in 1975 under the name of right trisegmentectomy. In 2006, Prof. Nagino from Nagoya reported so called “anatomic” right trisectionectomy focused on bile duct anatomy. For some cases of type IV hilar cholangiocarcinoma, R0 resection can be achieved with RTS, although it is not so easy. I use bilateral subcostal incision with median extension method for skin incision. After through exploration of abdominal cavity to detect the hidden metastasis, left hepatic artery was identified and preserved. Then, the dissection of hepatoduodenal ligament was performed to dissect the lymph node and perivascular soft tissues following common bile duct transaction at the suprapancreatic level. During upward dissection of bile duct and soft tissue including lymph node, right hepatic artery and right portal vein with several small portal vein branches to caudate process and spigelian lobe were dissected. After complete dissection of hepatoduodenal lig-ament, right hemi-liver and caudate were completely mobilized from IVC after right hepatic vein division. Then, parenchymal dissection of the liver along left portal plane was performed using CUSA and middle hep-atic vein was divided at the level of vena cava, also. Finally after several small portal vein to segment 4 were iden-tified and divided, bile duct to segment 4 was identified and left bile duct was divided at the level of the left side of the umbilical portion. Hepaticojejunostomy was constructed with interrupt suture using 5-0 vycryl. With regards to the outcome following right trisectionectomy for hilar cholangiocarcinoma, Berlin group have obtained best survival rate in trisectionectomy and portal vein resection group. They insisted that right trisectionectomy and portal vein resection should be regarded as the surgical procedure of choice, because of the tumor biology and anatomic considerations. We also have reported our data in 2008. Although there were many complications, we could get cancer free proximal margin in all case and no in-hospital mortality, fortunately. Moreover, 64.4% of high 5 year survival rate was achieved. When we analyzed 110 cases in SMC who underwent right sided hepatectomy, R0 resection rate was higher in right trisectionectomy group than in right- or extended right hemihepatectomy group, and 5 year survival rate was 55.7% when combined caudate lobectomy was carried out with right trisectionectomy. In conclusion, we should understand surgical anatomy of bile ducts and their relationship with surrounding vascular structure to achieve higher pathologically curative resection rate for hilar cholagiocarcinoma and right triectionectomy with caudate lobectomy may be procedure of choice for hilar cholangiocarcinoma to achieve R0 resection with higher survival rate. References 1. Klatskin G. Adenocarcinoma of the hepatic duct at its bifurcation within the porta hepatis. Am J Med 1965;38:241 2. Sakamoto E, Nimura Y, Hayakawa N, et al. The pattern of infiltration at the proximal border of hilar bile duct carcinoma: a histologic analysis of 62 resected cases. Ann Surg 1998;227:405-411 3. Ebata T Watanabe H, Ajoka Y, Oda K, Nimura Y. pathological appraisal of lines of resection for bile duct carcinoma. Br J Surg 2002;89:1260-1267 4. Neuhaus P, Jonas S, Bechstein WO, et al. Extended resections for hilar cholangiocarcinoma. Ann Surg 1999;230:808–818. 5. Neuhaus P, et al Oncological superiority of hilar en bloc resection for the treatment of hilar cholangiocarcinoma. Ann Surg Oncol 201;19:1602 6. Kawarada Y, et al. Surgical anatomy of the bile duct branches of the medial segment(B4) of the liver in relation to hilar carcinoma. J Hepatobiliary Pancreat Surg 2000;7:480 7. Starzl TE, et al. Hepatic trosegmentectomy and other liver resection. Surg Gynecol Obstet 1975;141:429 8. Nagino M et al. Anatomic right hepatic trisectionectomy(extended right hepatectomy) with caudate lobectomy for hilar cholangiocarcinoma. Ann Surg 2006;243:28 9. Paik KY, Choi DW, et al. Improved survival following right trisectionecromy with caudate lobectomy without operative mortality: Surgical treatment for hilar cholangiocarcinoma. J Gastrointst Surg 2008;12:1268 10. Song SC, Choi DW, et al. Surgical outcomes of 230 cases of resected hilar cholangiocarcinoma at a tertiary institution. ANZ J Surg 2013;83:268