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