1. Department of Surgery, Drammen Hospital, Vestre Viken HF, Drammen, Norway;
2. Department of Surgery, Lillehammer Hospital, Sykehuset Innlandet, Lillehammer, Norway;
3. Department of Pediatric and Gastrointestinal Surgery, Oslo University Hospital, Oslo, Norway;
4. Institute of Clinical Medicine, University of Oslo, Oslo, Norway;
5. Department of Gastroenterology, Oslo University Hospital, Oslo, Norway