Narrow Band Imaging for Diagnosis of Proximal Serrated Polyps

Although colonoscopy is considered the gold standard for diagnosis of colonic polyps, the missed rate for colonic adenoma ranged from 15-32%. In particular, missed colonic polyps in the right side colon have been suggested to be the cause for interval cancer that developed after a prior negative colonoscopy. Different endoscopic image enhanced modules like the narrow band imaging (NBI) have been developed to improve colonic polyp detection. However, it remains controversial whether the previous version of NBI helps to improve colonic polyp detection. The new generation colonoscope is equipped with high definition and improved narrow band imaging (NBI) which gives at least twice the viewable distance and contrast. The images obtained are far brighter with better resolution than the previous version. It however remains to be determined whether this enhanced imaging technique could help to improve colonic polyps detection. Hypothesis: The new generation NBI increases the detection rate of proximal serrated polyps and reduces the missed rate of all colorectal polyps. Aims: * To determine whether the new generation NBI improve the detection rate of proximal serrated polyps. * To determine whether the new generation NBI improve the detection rate of all colorectal adenoma and polyps. * To determine whether the new generation NBI reduce the miss rate of colorectal adenoma and polyps.