1. Department of Gastroenterology, The Affiliated Hospital of Qingdao University, Qingdao, P.R. China
2. Department of Gastroenterology, Shandong Second Provinical General Hospital, Jinan, P.R. China
3. Department of Gastroenterology, People’s Hospital of Rizhao, Rizhao, P.R. China
4. Department of Pathology, The Affiliated Hospital of Qingdao University, Qingdao, P.R. China