1. The School of Medicine, Nankai University, Tianjin, P.R. China
2. Department of Gastroenterology and Hepatology, Tianjin Union Medical Center Affiliated to Nankai University, Tianjin, P.R. China
3. Department of Gastroenterology and Hepatology, Tianjin Union Medical Center of Tianjin Medical University, Tianjin, P.R. China