Purpose: Combined resection of the caudate lobe of the liver is necessary to achieve curative resection for perihilar cholangiocarcinoma (PHCC). However, the location of the right boundary of the caudate lobe, which should be removed in the left-sided hepatectomy for PHCC, is still controversial. The aim of this study was to investigate the configuration of the portal and biliary branches in the dorsal sector using preoperative multidetector CT (MDCT) images in patients with PHCC and to clarify the optimal extent of the caudate lobe in the resection for PHCC. Methods: Between January 2008 and May 2012, 110 consecutive patients with PHCC underwent preoperative MDCT. The regions of the dorsal sector were classified as l-, b-, c-, d- and cp-region, according to the areas supplied by portal branches of the dorsal sector proposed by Couinaud, namely l, b, c, d and cp veins. The number and the ramification patterns of the portal (P-l, P-b, P-c, P-d, P-cp) and biliary (B-l, B-b, B-c, B-d, B-cp) branches in each region were investigated. Results: Eighty-five percent of P-d and 91% of B-d diverged from the anterior or posterior trunk, while 91% of P-c and 96% of B-c were from the left or right portal vein/hepatic duct. Ninety-eight percent of P-b and all of P-cp and P-l diverged from the first bifurcated branches. In addition, 92% of B-cp and all of B-b and B-l converged to the first bifurcated branches. Moreover, 61% of B-c and 35% of B-cp converged around the bifurcation of the anterior and posterior trunk. Conclusion: The boundary between c- and d-regions in the dorsal sector closely corresponds to the right margin of the caudate lobe, which was shifted to the d-region in 5-10% of cases. In left-sided hepatectomy with caudate lobectomy for PHCC, complete resection of the c-region and clearance of the confluence of the posterior/anterior bifurcation should be performed, while in cases in which the right margin shifted to the d-region, removal of the d-region should be considered.
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