GastrinsDuodenal NeoplasmsCalcium GluconateMultiple Endocrine Neoplasia Type 1Brunner GlandsPancreatic NeoplasmsSecretinAdenoma, Islet CellGlucagonomaEnterochromaffin CellsVagotomy, TruncalNeuroendocrine TumorsInsulinomaMultiple Endocrine NeoplasiaGastrectomyLiver NeoplasmsPancreaticoduodenectomyGastrinomaPeptic UlcerGastric AcidTomography, X-Ray ComputedNeoplasms, Multiple PrimaryFollow-Up StudiesProspective StudiesTreatment Outcome