1. Department of Surgery, Instituto de Investigación Sanitaria Aragón, Hospital Universitario Miguel Servet, 50009 Zaragoza, Spain
2. Department of Surgery, Hospital Santa Bárbara, 42005 Soria, Spain
3. Department of Surgery, Hospital HM Sanchinarro, 28050 Madrid, Spain
4. Department of Surgery, Hospital Universitario Miguel Servet, 50009 Zaragoza, Spain
5. Department of Surgery, Hospital Universitario de Guadalajara, 19002 Guadalajara, Spain
6. Department of Surgery, Hospital General Universitario Dr. Balmis, 03010 Alicante, Spain