1. Visceral Surgery; Hirslanden Klinik St. Anna; Luzern Switzerland
2. University Basel; Basel Switzerland
3. Department of Visceral and Thoracic Surgery; Cantonal Hospital of Winterthur; Winterthur Switzerland
4. Department of Pediatric Surgery; Children's University Hospital; Basel Switzerland
5. Gastrointestinal Surgery; Royal North Shore Hospital; St. Leonards Australia
6. Epidemiology, Biostatistics and Prevention Institute; University of Zurich; Zurich Switzerland