1. Department of Medicine, Section for Gastroenterology, Stord Helse-Fonna Hospital, Stord, Norway;
2. Department of Clinical Medicine, University of Bergen, Bergen, Norway;
3. Department of Medicine, National Centre for Functional Gastrointestinal Disorders, Haukeland University Hospital, Bergen, Norway;
4. Department of Medicine, GI Motility Research Unit, Division of Gastroenterology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand;
5. King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand;
6. Department of Medicine, National Centre for Ultrasound in Gastroenterology, Haukeland University Hospital, Bergen, Norway