Colonoscopy is the "gold standard" technique for diagnosis and treatment of colonic lesions. Moreover, high definition colonoscopes (HD) associated to digital chromoendoscopy had shown better results regarding adenoma and polyps detection when compared to standard non HD scopes. However, evidence shows that during standard colonoscopy many lesions could be missed, including polyps, cancer and other kind of lesions. This could be correlated to many factors and recently reports show evidence that lesions behind the folds could be missed because the limitation of a forward view examination. Until know, a new auxiliary imaging device called "Third Eye Retroscope" had demonstrated more lesions detection during colonoscopy using a retro view, but with some limitations as absence of HD vision, the need of additional equipment and the fact the device occupies the accessory channel, limiting therapeutic efficiency. Recently a new HD colonoscope called "RETROVIEW" (PENTAX Medical) has been developed. It permits visualization of colonic mucosa in forward view, in retroflex view and allows for performance of diagnostic and therapeutics in a single colonoscope.

Primary outcome:

To determine the safety and feasibility of the retro view during colonoscopy using RETROVIEW colonoscope. Safety was measured by the number of bleeding or perforation rates as adverse event during the procedure. Feasibility was measured by the number of cases that is possible to achieve a retroflexion in the colon Secondary outcome: withdrawal phase time and total procedure time.

Inclusion Criteria:

• undergoing colonoscopy for colorectal neoplasia screening, for polyp surveillance, or for diagnostic workup including anemia, abdominal pain, constipation, abnormal imaging; and if they were able to understand and provide written consent for the procedure.

Exclusion Criteria:

• age <18; pregnancy, included history of colon resection, known inflammatory bowel disease, polyposis syndrome, radiation therapy to abdomen or pelvis, suspicion of chronic stricture potentially precluding complete colonoscopy, presence of diverticulitis or toxic megacolon, hemophilia and concurrent enrollment in another clinical investigation.

consecutive patients undergoing for colonoscopy at the Instituto Ecuatoriano de Enfermedades Digestivas