[1] Hokkaido PWFAC Asahikawa Kosei Gen Hosp, Div Surg, Asahikawa, Hokkaido 788211, Japan
[2] Hokkaido PWFAC Asahikawa Kosei Gen Hosp, Gastroenterol Endoscop Ctr, Asahikawa, Hokkaido 788211, Japan
[3] Asahikawa Med Univ, Dept Pathol, Asahikawa, Hokkaido 788510, Japan