1. Division of Colon and Rectal Surgery, Shizuoka Cancer Center Hospital, Shizuoka, Japan.
2. Arakawa Clinic of Proctology, Tokyo, Japan.
3. Department of Anatomy, Akita University School of Medicine, Akita, Japan.
4. Department of Anatomy and Embryology II, Faculty of Medicine, Complutense University, Madrid, Spain.
5. Division of Internal Medicine, Iwamizawa Kojin-Kai Hospital, Iwamizawa, Japan.
6. Department of Surgical Oncology, Graduate School, Tokyo Dental and Medical University, Tokyo, Japan.