Comparison of Colonoscopy With Virtual Chromoendoscopy Using 3rd Generation NBI System to Chromoendoscopy With Indigo Carmine in Lynch Patients.

Chromoendoscopy using indigo carmine dye is recommended every 1 to 2 years in patients having Lynch Syndrome (LS). However, it is a time-consuming procedure, requiring a prior learning and has an additional cost, the reason why it is not yet systematically practiced in all endoscopy centers. The "Narrow Band Imaging" (NBI) is a recent virtual chromoendoscopy technique using optical filters at the light source of the endoscope to highlight the vascular structures of the mucosa by pressing a button. NBI is currently used to better characterize dysplasia lesions in the esophageal, gastric, and colon mucosa. A new generation (3rd generation) of NBI is currently available on some endoscopes, it can deliver more brightness and contrast, and could allow for better detection of flat lesions. Until today, no study has directly compared colonic chromoendoscopy with Indigo carmine to virtual chromoendoscopy with NBI (3rd generation) in LS patients. The hypothesis that this research aims to verify is that the new generation NBI system might do at least as well as indigo carmine in colonic adenoma detection in LS. This study aims to compare colonoscopy with virtual chromoendoscopy using 3rd generation NBI system to chromoendoscopy with indigo carmine in LS patients, in a back-to-back, prospective non inferiority design, in which all patients will have both techniques in the following order: NBI first followed by Indigo carmine.