1 National Clinical Research Center for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China.
2 Department of Gastroenterology, Langzhong People's Hospital, Langzhong, Sichuan, China.
3 National Clinical Research Center for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China. Electronic address: yanglinpan@hotmail.com.