1. Department of Surgery, Oulu University Hospital, Oulu, Finland
2. Division of Operative Care, Oulu University Hospital and Medical Research Center Oulu, University of Oulu, Oulu, Finland
3. Division of Digestive Surgery and Urology, Turku University Hospital, Turku, Finland
4. Department of Surgery, University of Turku, Turku, Finland
5. Department of Surgery, Kuopio University Hospital, Kuopio, Finland
6. Department of Surgery, Seinäjoki Central Hospital, Seinäjoki, Finland
7. Division of Surgery, Gastroenterology and Oncology, Tampere University Hospital, Tampere, Finland
8. Department of Biostatistics, University of Turku, Turku, Finland