1. Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
2. The Fourth Department of the Digestive Disease Center, Suining Central Hospital, Suining, Sichuan 629000, P.R. China
3. Special Key Laboratory of Oral Disease Research, Higher Education Institution in Guizhou Province, School of Stomatology, Zunyi Medical University, Zunyi, Guizhou 563006, P.R. China