1 Department of General Surgery, Chiba University Graduate School of Medicine, Chiba, Japan. Electronic address: i-hosokawa@umin.ac.jp.
2 Department of General Surgery, Chiba University Graduate School of Medicine, Chiba, Japan.
3 Narita Hospital, International University of Health and Welfare, Chiba, Japan; Department of General Surgery, Chiba University Graduate School of Medicine, Chiba, Japan.