Current concepts of chronic gastritis and gastropathies: new international consensus RE.GA.IN. Review

Recent decades have been marked by several important milestones in the field of gastritis. New epidemiological reports were received, especially from countries with a high incidence of gastric cancer, and H. pylori infection was recognized as the most important cause of gastritis, due to which it was quickly included among the primary infectious oncogenic agents. Clinical strategies for the detection and eradication of H. pylori infection were developed, the previously unsuspected clinical and pathological significance of the gastric microbiota was established, and extraordinary progress was made in the technology of esophagogastroduodenoscopy. Histological determination of gastritis from the point of view of «stage» (that is, risk stratification of stomach cancer) has entered clinical practice. In addition to the Sydney and Houston gastritis classifications, six editions of the Maastricht Consensus (1996—2022) and the Kyoto Global Consensus deserve special attention, thanks to which agreements were reached in the most controversial issues of the entire spectrum of gastritis, with a special emphasis on H. pylori gastritis, which accounts for more than 90% of all forms of gastritis worldwide. The Real‑world Gastritis Initiative (RE.GA.IN) marks the next step in the ongoing quest to achieve a better understanding of various gastric conditions. The RE.GA.IN consensus was concluded in Venice in November 2022 after 8 months of intensive global scientific reasoning. RE.GA.IN’s mission itself has been focused on critically reviewing, updating, sharing and building consensus on the current scientific knowledge of inflammatory gastric lesions. It includes eight sections on clinicopathological topics, each consisting of preamble, which briefly presents the following statements and corresponding explanatory texts. For each statement, the level of evidence (assessed according to a predefined four‑level scale) and the strength of recommendations according to the GRADE system are reported. The following topics were considered in the consensus: 1) definition and problem of classification of gastritis; 2) spectrum of H. pylori gastritis; 3) key diagnosis of H. pylori gastritis; 4) H. pylori gastritis: clinical results; 5) autoimmune gastritis; 6) gastritis of low prevalence; 7) gastritis and gastric microbiota; 8) epidemiology of gastritis and associated precancerous and neoplastic lesions. Thus, the most controversial aspects of gastritis were addressed and a comprehensive and diverse body of knowledge was brought together to use patient‑oriented evidence to assist physicians in their clinical practice.