1 Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, Niigata, Japan. shimaday@med.niigata-u.ac.jp.
2 Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, Niigata, Japan.
3 Department of Obstetrics and Gynecology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.