Dye-based chromoendoscopy versus i-scan virtual chromoendoscopy in long-standing ulcerative colitis: Multicenter prospective RCT - Alexander Jans; Pieter Sinonquel; Tom C.J. Seerden; Alexander De Bodelier; Rogier de Ridder; Marieke J Pierik; John Gásdal Karstensen; Stine Sloth; Gert De Hertogh; Ingrid Demedts; Hilde Willekens; Severine Vermeire; et al. (Endoscopy International Open)