1. Department of Digestive Diseases; Hospital Universitario Marqués de Valdecilla and Marqués de Valdecilla Research Institute (IDIVAL); Santander Spain
2. Department of Digestive Diseases; Complejo Hospitalario de La Rioja; Logroño Spain
3. Department of Digestive Diseases; Hospital de León; León Spain
4. Department of Digestive Diseases; Hospital Universitario Central de Asturias; Oviedo Spain
5. Department of Digestive Diseases; Hospital San Agustín; Avilés-Asturias Spain
6. Department of Digestive Diseases; Hospital de Cabueñes; Gijón-Asturias Spain
7. Department of Digestive Diseases; Hospital Universitario Río Hortega; Valladolid Spain
8. Department of Digestive Diseases; Hospital Universitario de Burgos; Burgos Spain
9. Department of Digestive Diseases; Hospital Clínico Universitario de Valladolid; Valladolid Spain
10. Department of Digestive Diseases; Hospital Universitario de Salamanca; Salamanca Spain
11. Department of Digestive Diseases; Complejo Asistencial de Zamora; Zamora Spain
12. Department of Digestive Diseases; Hospital Comarcal de Laredo; Laredo-Cantabria Spain
13. Department of Digestive Diseases; Hospital Comarcal Sierrallana; Torrelavega-Cantabria Spain
14. Department of Digestive Diseases; Hospital Río Carrión; Palencia Spain
15. Department of Digestive Diseases; Hospital Álvarez-Buylla; Mieres-Asturias Spain
16. Department of Digestive Diseases; Hospital Valle del Nalón; Langreo-Asturias Spain