1. Department of Gastroenterology, Shanxi Medical University, Taiyuan, Shanxi 030000, P.R. China
2. Department of Gastroenterology, Shanxi Datong University Affiliated Cancer Hospital, Datong, Shanxi 037000, P.R. China
3. Department of Gastroenterology, The First Hospital of Shanxi Medical University, Taiyuan, Shanxi 030000, P.R. China