Gastroenterologìa (Feb 2017)
Modern endoscopic techniques of precancerous stomach conditions diagnostics: problems and possibilities
Abstract
The review shows the classification of precancerous stomach pathology, proposed in the Consensus Management of precancerous conditions and lesions in the stomach (MAPS) (2012), according to which they are divided into precancerous lesions (atrophic gastritis and intestinal metaplasia) and precancerous changes (stomach mucosa dysplasia). Chronic atrophic gastritis and intestinal metaplasia are considered precancerous conditions, as they are the background for development of dysplasia and gastric adenocarcinoma of intestinal type. Precancerous changes is gastric dysplasia and is the penultimate stage of gastric carcinogenesis sequence and is defined as histologically clear tumor epithelium without signs of infection, and thus is a direct tumor precancerous lesions. It is noted that, in general, the risk of stomach cancer is too small to justify by endoscopic observation in all the patients with atrophic gastritis and intestinal metaplasia. Thus, it is necessary to define additional risk factors for stomach cancer progression in that it is presented in the Kyoto global consensus on Helicobacter pylori-associated gastritis (2015) for this category of patients. It was determined that stomach cancer risk factors are the intragastric distribution and the extent of intestinal metaplasia, presence of a family history of gastric cancer, the definition of subtypes of intestinal metaplasia. Sydney system is used for chronic gastritis classification (Houston review), as well as classification by metaplasia type (non-metaplastic, metaplastic atrophy of uncertain type). There are three methods to determine the prevalence and extent of atrophic gastritis and intestinal metaplasia used: endoscopic, histological and serological. The atrophy severity of the gastric mucosa is determined histologically. Classification of atrophy severity by endoscopic parameters does not currently exist. Intestinal metaplasia developed in different parts of the stomach and is multifocal (in the antrum, along the small curvature of the stomach diffusely). According to the researchers’ data, the presence of the intestinal metaplasia on the lesser curvature of the stomach has a strong association with cancer risk. The different kinds of endoscopic devices allow diagnostically diffentiate atrophy and intestinal metaplasia of the stomach. Endoscopy white light can’t reliably diagnose stomach precancerous changes, while videoendoscopy with magnifications and narrow band imaging (NBI), according to researchers’ data, significantly improves the diagnosis of this disease. The basis of diagnosis is increasing verification of two main structures: the architectonic subepithelial microvascular network microstructure and mucosal surface, which has a different pattern in the body and antral stomach. But to date there is no common classification of changes to these structures in various pathological changes. There are a large number of classifications of changes in endoscopy with NBI mode and optical zoom: Yagi (2002), M. Dinis-Ribeiro (2003), G.K. Anagnostopoulos et al. (2007), T. Tahara (2009), P. Pimentel-Nunes, M. Dinis-Ribeiro (2012). It is noted that the problem is that NBI with zoom is practically impossible to use in daily clinical practice, the method requires a certain level of knowledge and endoscope type, available only in several centers, as well as the use of sedation for maximum effective inspection.
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