1. Department of Gastrointestinal Surgery, Stavanger University Hospital, Stavanger, Norway;
2. Department of Clinical Medicine, University of Bergen, Bergen, Norway;
3. Department of Surgery, Academic Medical Center, Amsterdam, the Netherlands;
4. Division of Epidemiology and Public Health, School of Community Health Sciences, University of Nottingham, Nottingham, UK;
5. Division of Trauma Emergency Surgery and Surgical Critical Care, Massachusetts General Hospital, Boston, MA, USA;
6. Harvard Medical School, Boston, MA, USA