1. Clinical Hospital Centre Rijeka; Department of Gastroenterology; Kresimirova 42 Rijeka Croatia 51000
2. Royal Free Campus, UCL Medical School; Department of Surgery; Royal Free Hospital Rowland Hill Street London UK NW3 2PF
3. University of Birmingham; Public Health, Epidemiology and Biostatistics; Edgbaston Birmingham UK B15 2TT
4. North Bristol NHS Trust; Frenchay Hospital Bristol UK BS16 1LE