Assessment of colorectal polyp detection along the short-axis direction of the intestinal lumen during colonoscopic observation: a retrospective study in Japan

Colorectal polyp detection during colonoscopy is influenced by the lesion location, size, morphology, and histology. However, no studies have systematically assessed the difficulty of detection along the short axis of the intestinal lumen. This study aimed to evaluate the colorectal polyp detection rates on this axis during colonoscopy. This retrospective study analyzed 1,169 polyps in 513 patients who underwent colonoscopy at Showa University Hospital between November 2022 and February 2023. The short-axis lumen was divided into: upper right, lower right, lower left, and upper left. Each polyp detected was assigned to a quadrant. Detection rates were compared across quadrants and analyzed for associations with clinicopathological factors including lesion size, location, macroscopic type, and examiner experience. The lesion detection rates varied significantly by quadrant. The upper left quadrant had the lowest detection rate (17.5%) compared with the expected 25.0% per quadrant. Subgroup analyses consistently confirmed the lower detection rates in this quadrant across most lesion types and patient groups, except for lesions in the cecum and rectum. The lower detection rate in the upper left quadrant suggests that this orientation poses a challenge and may increase the number of missed lesions. Enhanced examination of this area may improve detection; however, further prospective studies are required.