1. Gastroenterology Section and Endoscopy Unit, Hospital del Salvador and Faculty of Medicine, Universidad de Chile, Santiago, Chile
2. Rio Grande do Sul Foundation of Gastroenterology (FUGAST), Porto Alegre, Brazil
3. Departments of Surgery and Anatomy, Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil