A comparison of magnifying and nonmagnifying colonoscopy for diagnosis of colorectal polyps: a prospective study

Background: Discrimination between neoplastic and non-neoplastic colorectal polyps is essential for determining appropriate treatment. The mucosal crypt pattern of polyps can be observed with a nonmagnifying colonoscope; however, mucosal crypt patterns are better seen by magnifying colonoscopy, which can also be a noninvasive means for predicting histopathology. This study prospectively compared the ability to distinguish between neoplastic and non-neoplastic lesions by magnifying and nonmagnifying colonoscopy. Methods: Six hundred sixty patients were randomly assigned to undergo magnifying or nonmagnifying colonoscopy (2 groups each of 330 patients). The mucosal crypt pattern of colorectal lesions was classified into types I through V after spraying with 0.2% Indigo carmine dye. The histopathology of all lesions was confirmed by evaluation of endoscopic resection specimens or biopsy specimens. Only lesions 10 mm or less in diameter were included in the study. Results: The accuracy of magnifying colonoscopy in distinguishing neoplastic from non-neoplastic lesions (92%, 372/405) was significantly higher than for nonmagnifying colonoscopy (68%, 278/407). Insertion of magnifying and nonmagnifying colonoscopes to the cecum was successful in, respectively, 321 patients (97%) and 317 patients (96%), with no significant differences in the average time to reach the cecum or average total procedure time. No serious complication was observed during or immediately after the examinations. Conclusions: Observation of mucosal crypt pattern with magnifying colonoscopy is superior to nonmagnifying colonoscopy for distinguishing between neoplastic and non-neoplastic colorectal lesions.