Gastritis is defined histological by various stages of inflammatory changes. These include infiltration of inflammatory cells into the lamina propria often combined with alteration and defects of the mucosal surface such as erosions. Helicobacter pylori or nonsteroidal anti-inflammatory drugs (NSAIDs) can induce gastritis. The former can lead to atrophic gastritis and intestinal metaplasia, which increase the risk for the development of gastric cancer. Helicobacter pylori and intestinal metaplasia can be easily identified using confocal laser endomicroscopy [Guo et al. 2008, Zhang et al. 2008]. Helicobacter pylori can be found on the surface of the gastric mucosa [Kiesslich et al. 2005]. Thus, acriflavine as a topical contrast agent has to be used to identify Helicobacter pylori. Intestinal metaplasia can be best seen using fluorescein. The tissue looks much brighter compared to the surrounding normal mucosa and characteristic goblet cells can be identified due to their characteristic target phenomenon. Endomicroscopy is ideally suited to diagnose intestinal metaplasia in patients with atrophic gastritis. Furthermore, Helicobacter pylori can be identified in viva and distinct cellular and vascular changes guide biopsies towards neoplastic changes
The endoscopic detection of early gastric cancer is challenging because most of the lesions are usually non-polypoid. Fluorescein-guided endomicroscopy is particularly good at demonstrating the blood vessel architecture, which can be used to differentiate between non-neoplastic and neoplastic lesions. The vessel function can be observed and leakage of fluorescein into the lamina propria characterizes inflammation or neo-angiogenesis [Liu et al. 2008]. Endomicroscopy allows immediate microscopic analysis of the gastric mucosa during ongoing endoscopy. Comparison of regular and altered gastric mucosa facilitates the interpretation of the confocal images. Changes in tissue and microscopic blood vessel architecture as well as changes in cell morphology are valuable endomicroscopic criteria to define neoplasia. Nuclear changes can best be observed using Acriflavine as topical contrast agent [Kakeij et al. 2006].
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