1. Department of Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA
2. Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
3. Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialties, PROMISE, Gastroenterology and Hepatology Unit, University of Palermo, Palermo, Italy
4. Department of Medicine, Division of Gastroenterology, Modena Hospital, University of Modena and Reggio Emilia, Modena, Italy
5. Department of Medicine, Division of Gastroenterology and Hepatology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA