TWICE trial

Interventions: Additional forward view examination in the right colon with narrow-band imaging (Control group) Standard withdrawal colonoscopy group; Standard forward view examination in the whole colon with white-light imaging (Test group) Second forward view with narrow-band imaging group; Second forward view examination of the right colon with narrow-band imaging after the first right-colon examination with white-light imaging Primary outcome(s): Adenoma detection rate in the right colon Study Design: randomized controlled trial, open(masking not used), active control, parallel assignment, diagnostic purpose