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.