1. Department of Gastroenterology, Puerta de Hierro University Hospital, Majadahonda, Spain
2. Department of Surgery, Puerta de Hierro University Hospital, Majadahonda, Spain
3. Department of Gastroenterology, La Princesa University Hospital, Madrid, Spain
4. Department of Anesthesia, Puerta de Hierro University Hospital, Majadahonda, Spain
5. Center of Endoscopic Research and Therapeutics, University of Chicago Medical Center, Chicago, Illinois, USA
6. Department of Surgery, Infanta Sofía Hospital, Alcobendas, Spain