[1] Univ Tokyo, Grad Sch Med, Div Hepato Biliary Pancreat Surg, Dept Surg,Bunkyo Ku, Tokyo 1138655, Japan
[2] Univ Tokyo, Grad Sch Med, Div Hepato Biliary Pancreat Surg, Dept Biostat, Tokyo, Japan
[3] Nihon Univ, Dept Digest Surg, Sch Med, Tokyo, Japan