Usefulness of magnifying narrow-band imaging endoscopy for the diagnosis of gastric and colorectal lesions.

A series of studies about the potential usefulness of magnifying endoscopy with narrow-band imaging (NBI) for the diagnosis of gastric and colonic lesion is reviewed. Concerning the magnifying NBI appearances of gastric lesions, a light blue crest is a highly accurate sign of the presence of histological intestinal metaplasia. Also, the degree of irregularity of the mucosal and vascular pattern is correlated with the histological severity of Helicobacter pylori-associated chronic gastritis. According to the 'VS classification', an irregular microvascular pattern and/or an irregular microsurface pattern together with a clear demarcation line are characteristic for early gastric carcinoma, and a multicenter prospective randomized controlled trial demonstrated that magnifying endoscopy with NBI is superior to ordinary white light endoscopy for making a differential diagnosis of a small depressed lesion between carcinoma and non-carcinoma. Concerning the magnifying NBI appearances of colonic tumor, the vague or invisible microvascular pattern is mostly observed in hyperplastic polyp. The regular meshed microvascular pattern is mostly observed in adenoma. The irregular meshed microvascular pattern is mostly observed in intramucosal or shallow submucosal-invasive carcinoma. The decreased or loose microvasucular pattern is mostly observed in deep submucosal-invasive carcinoma. Thus, magnifying NBI endoscopy is useful for the differentiation of colorectal non-adenomatous lesions from adenoma, the differentiation of adenoma from carcinoma, and the assessment of invasion depth of early colorectal carcinoma. At present, several magnifying NBI classifications for the diagnosis of early colorectal neoplasia have been proposed in Japan. Recently, the NICE classification based on NBI findings with/without magnification for colorectal tumor was established by an international group.