[1] Peking Univ Third Hosp, Dept Gastroenterol, Beijing, Peoples R China
[2] Peking Univ Third Hosp, Res Ctr Clin Epidemiol, Beijing, Peoples R China
[3] Peking Univ Third Hosp, Dept Ultrasound, Beijing, Peoples R China
[4] Peking Univ Third Hosp, Dept Gastroenterol, 49 N Garden Rd,Haidian Dist, Beijing 100191, Peoples R China