1. Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
2. Department of Gastroenterology, Longgang District People's Hospital, Shenzhen, Guangdong 518172, P.R. China
3. Department of Gastroenterology, The Second Affiliated Hospital University of South China, Hengyang, Hunan 421001, P.R. China
4. Department of Gastroenterology, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong 510150, P.R. China