Division of Gastroenterology and Hepatology;
Department of Internal Medicine;
Keio University School of Medicine;
Endoscopy Center;
NHO Kurihama Medical and Addiction Center;
Colonoscopy; Water; immersion; Waterexchange; Underwater; Unsedated; Sigmoid; volvulus; Detorsion; Polypectomy; Gastrointestinal; bleeding; Irritable; bowel; syndrome;