atrophic gastritis treatmentatrophic hyperplastic gastritismetaplastic atrophic gastritischronic atrophic gastritismultifocal atrophic gastritisdiffuse atrophic gastritisatrophic gastritis reversibleatrophic antral gastritismild atrophic gastritisautoimmune chronic atrophic gastritissevere chronic atrophic gastritisatrophic gastritis pathology outlines