GastritisGastric MucosaGastritis, AtrophicHelicobacter pyloriHelicobacter InfectionsPyloric AntrumMetaplasiaStomach UlcerStomachStomach NeoplasmsChronic DiseasePeptic UlcerGastroscopyStomach DiseasesPepsinogen AGastrinsAchlorhydriaGastric JuiceDuodenal UlcerDyspepsiaBiopsyDuodenitisBile RefluxPepsinogen CGastritis, HypertrophicHelicobacterHelicobacter heilmanniiUreaseIntestinal MucosaHelicobacter felisPrecancerous ConditionsCampylobacterParietal Cells, GastricEndoscopy, GastrointestinalAtrophyAnti-Ulcer AgentsAntigens, BacterialGastric AcidPepsinogensBacterial ProteinsAmoxicillinOmeprazoleDuodenumLymphoma, B-Cell, Marginal ZoneAnemia, PerniciousMouth MucosaAntibodies, BacterialCampylobacter InfectionsImmunohistochemistryGastric FundusH(+)-K(+)-Exchanging ATPasePostgastrectomy SyndromesLewis Blood-Group SystemClarithromycinPolymerase Chain ReactionGastrin-Secreting CellsAdenocarcinomaGastric MucinsCytotoxinsEndoscopyGastric EmptyingGenotypeNasal MucosaIntestinesPylorusDuodenogastric RefluxChoristomaHyperplasiaEndoscopy, Digestive SystemGastric Acidity DeterminationIntrinsic FactorImmunoglobulin GPentagastrinAcinonyxMucous MembraneDNA, BacterialImmunoglobulin AAnti-Bacterial AgentsHydrochloric AcidCase-Control StudiesAutoimmune DiseasesGastric Antral Vascular EctasiaEpithelial CellsBismuthDrug Therapy, CombinationMicroscopy, ElectronGastrointestinal HemorrhageGastrectomyGastrointestinal MotilityPrevalenceFollicular AtresiaMexicoEnzyme-Linked Immunosorbent Assay