1. Department of Gastroenterology, Tsaritsa Yoanna University Hospital, Medical University of Sofia, Bulgaria
2. Gastroenterology and Endoscopy Unit, S. Elia-Raimondi Hospital, Caltanissetta, Italy
3. Digestive Disease Center, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Catholic University of Sacred Heart, Rome, Italy