Middle hepatic vein (MHV) reconstruction with an interposition vessel graft has been settled as a standard procedure for living donor liver transplantation (LDLT) using a right lobe graft. Increasing demand of vessel graft in the situation of limited resources of allograft led the investigators to search for new vessel substitutes. Since the use of thin-walled expanded polytetrafluoroethylene (PTFE) graft showed poor long-term patency, a prospective study is going to be performed to enhance the clinical usability of expanded PTFE graft. A clinical study intends to know how to maintain its luminal flow effectively by using ringed PTFE graft. During 12 months of study period, ringed PTFE graft will be used for reconstruction of MHV reconstruction. The investigators expect that ringed PTFE graft seems to be a more useful alternative than usual PTFE graft when adequate autologous or allogenic vessel graft is not available.