[1] John Radcliffe Hosp, Gastroenterol Unit, Oxford OX3 9DU, England
[2] Hosp Zvezdara, Dept Gastroenterol, Belgrade, Serbia
[3] Barts & London Queen Marys Sch Med & Dent, London, England
[4] John Radcliffe Hosp, Dept Cellular Pathol, Oxford OX3 9DU, England
[5] John Radcliffe Hosp, Colorectal Surg Unit, Oxford OX3 9DU, England