1. Department of Gastroenterology, Oslo University Hospital, Oslo, Norway;
2. Institute of Clinical Medicine, University of Oslo, Oslo, Norway;
3. The Intervention Centre, Oslo University Hospital, Oslo, Norway;
4. Department of Surgery N1, Yerevan State Medical University after M. Heratsi, Yerevan, Armenia;
5. Central Clinical Military Hospital, Yerevan, Armenia;
6. Department of Hepato-Pancreato-Biliary Surgery, Oslo University Hospital, Oslo, Norway;
7. Department of Pathology, Oslo University Hospital, Oslo, Norway