1. Scandinavian Surgical Outcomes Research Group, Department of Surgery, Sahlgrenska University Hospital/Östra, Sahlgrenska Academy, Gothenburg University, Gothenburg, Sweden
2. Department of Surgery, Alingsås Hospital, Alingsås, Sweden
3. Department of Surgery, VU University Medical Centre, Amsterdam, The Netherlands
4. Department of Surgery, Roskilde Hospital, Roskilde, Denmark
5. Department of Surgery, Herlev Hospital, Copenhagen University, Copenhagen, Denmark