Graduate School, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China; Department of Gastroenterology, China-Japan Friendship Hospital, Beijing, China. Department of Gastroenterology, China-Japan Friendship Hospital, Beijing, China. Department of Gastroenterology, China-Japan Friendship Hospital, Beijing, China; Graduate School, Beijing University of Chinese Medicine, Beijing, China. Graduate School, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China; Department of Gastroenterology, China-Japan Friendship Hospital, Beijing, China. Electronic address: shukunyao@126.com.