1. Department of Digestive Surgery, Akershus University Hospital, Lorenskog, Norway
2. Department of Digestive Surgery, St Olavs Hospital, Trondheim University Hospital, Trondheim, Norway
3. Institute of Clinical Medicine, Campus Ahus, University of Oslo and Health Services Research Unit, Akershus University Hospital, Lorenskog, Norway
4. Department of Radiology, Akershus University Hospital, Lorenskog, Norway
5. Medical Faculty, University of Oslo, Oslo, Norway