1 Department of Gastroenterology, Hospital Universitario Rio Hortega, Valladolid, Spain.
2 Department of Gastroenterology, Hospital Santos Reyes, Aranda de Duero, Burgos, Spain.
3 Department of Pathology, Complejo Asistencial Universitario de Salamanca, Salamanca, Spain.
4 Department of Gastroenterology, Complejo Asistencial Universitario de Salamanca, Salamanca, Spain.
5 Department of Gastroenterology, Hospital de Medina del Campo, Valladolid, Spain.
6 Department of Gastroenterology, Hospital Río Carrión, Palencia, Spain.
7 Department of Gastroenterology, Hospital Universitario de Fuenlabrada, IdiPAz (Instituto de investigación Hospital Universitario La Paz), Madrid, Spain.
8 Department of Gastroenterology, Hospital General de Segovia, Segovia, Spain.