1 Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Japan.
2 Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Japan yhayakawa-tky@umin.ac.jp niikura-dky@umin.ac.jp.
3 Department of Gastroenterological Endoscopy, Tokyo Medical University, Shinjuku-ku, Japan.