1. Faculty of Medicine, Department of Clinical Medicine, University of Oslo, Oslo, Norway;
2. Department of Medicine, National Centre for Functional Gastrointestinal Disorders, Haukeland University Hospital, Bergen, Norway;
3. Department of Medicine, Haukeland University Hospital, Bergen, Norway;
4. Clinical institute 1, University of Bergen, Bergen, Norway;
5. Department of Transplantation Medicine, Section for Gastroenterology, Oslo University Hospital, Oslo, Norway