1 Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
2 Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; Department of Hepato-Biliary-Pancreatic Medicine, The Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan.
3 Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; Department of Endoscopy and Endoscopic Surgery, The University of Tokyo Hospital, Tokyo, Japan.