1. Department of Gastroenterology, Ningxia Hui Autonomous Region People's Hospital, Yinchuan, Ningxia Hui Autonomous Region 750021, P.R. China
2. Department of General Medicine, General Hospital of Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China
3. Department of Gastroenterology, The Second People's Hospital of Linyi, Linyi, Shandong 276000, P.R. China
4. Department of Gastroenterology, Xijing Hospital of Digestive Diseases, State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xi'an, Shaanxi 710000, P.R. China