1. Department of Pediatric Surgery, Hospital Universitario de Navarra, Pamplona, Navarra, Spain
2. Department of Preventive Medicine and Public Health, School of Medicine, University of Navarra, Pamplona, Navarra, Spain
3. Department of Pediatrics, Hospital Universitario de Navarra, Pamplona, Navarra, Spain
4. Department of Pathology, Hospital Universitario de Navarra, Pamplona, Navarra, Spain
5. Department of Pathology, Hospital Universitario de Araba, Vitoria-Gasteiz, Spain