Felix W Leung1, Hui Jia2. 1. Division of Gastroenterology, Department of Medicine, Sepulveda Ambulatory Care Center, VAGLAHS and David Geffen School of Medicine at UCLA, North Hills and Los Angeles, California, USA. 2. Division of Gastroenterology, Department of Medicine, Sepulveda Ambulatory Care Center, VAGLAHS and David Geffen School of Medicine at UCLA, North Hills and Los Angeles, California, USA; Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, Shaanxi, China.