Endoscopic diagnosis of gastric intestinal metaplasia

Long-standing Helicobacter pylori infection causes chronic inflammation in the gastric mucosa, induces biomolecular alteration and transforms gastric mucosa into epithelium having the intestinal phenotype. This phenomenon is called intestinal metaplasia. Because both intestinal metaplasia and gastric cancer develop through chronic Helicobacter pylori infection, and intestinal metaplasia and a portion of differentiated-type gastric cancers have a common development pathway, intestinal metaplasia is important as a para- and pre-neoplastic condition of gastric carcinoma. Intestinal metaplasia, together with atrophy, initially develops as multiple foci in the lesser curvature near the incisura angularis and at the border of the antrum and the body in the anterior and posterior walls. Then, new independent foci appear along the lesser curvature of the body and, later, in the anterior and posterior walls. The multiple foci coalesce, resulting in extensive areas of atrophy with intestinal metaplasia, which finally may involve most of the gastric mucosa. The microsurface structure of normal gastric mucosa appears as the foveola type in the body and the groove type in the antrum, whereas the microsurface structure of intestinal metaplasia shows the groove type or villiform structures that mimic the normal antral or intestinal mucosa. Intestinal metaplasia looks whitish on white light endoscopy, and narrow band imaging contrasts color difference because of 1) the white opaque substance that obscures subepithelial capillaries, 2) light blue crest that reflects short wavelength light on the surface of the epithelium, 3) marginal turbid band that makes the epithelium cloudy, and 4) decreased vascular density due to different mucosal structure. Endoscopy enables us to observe the actual prevalence and distribution of intestinal metaplasia, to perform targeted biopsy and to bridge macroscopic findings, histological findings and biomolecular findings of lesions in the stomach. Consequently, understanding the endoscopic finding of gastric intestinal metaplasia increases the yield of endoscopy when investigating the pathogenesis of chronic gastritis and gastric carcinogenesis.