1 Department of Gastroenterology, Faculty of Medicine, Academy of Silesia, Katowice, Poland; Endoterapia, H-T Centrum Medyczne, 43-100 Tychy, Poland.
2 Department of Gastroenterology, Faculty of Medicine, Academy of Silesia, Katowice, Poland; Endoterapia, H-T Centrum Medyczne, 43-100 Tychy, Poland. Electronic address: marcin.romanczyk@htcentrum.pl.
3 Clinical Effectiveness Research Group, University of Oslo and Oslo University Hospital, Oslo, Norway; Gastroenterology Section, Department of Transplantation Medicine, Oslo University Hospital, Oslo, Norway; Digestive Disease Center, Showa University Northern Yokohama Hospital, Yokohama, Japan.