Gastrointestinal NeoplasmsUpper Gastrointestinal TractStomach NeoplasmsGastrointestinal TractEsophageal NeoplasmsPancreatic NeoplasmsDigestive SystemAdenocarcinomaGastrointestinal DiseasesEndoscopy, GastrointestinalGastrointestinal HemorrhageColorectal NeoplasmsDuodenitisFluorouracilStomachEsophageal DiseasesCausticsDuodenal NeoplasmsEndoscopyDuodenoscopyGastroscopyLiver NeoplasmsDuodenumStomach DiseasesColonic NeoplasmsBurns, ChemicalEndoscopes, GastrointestinalPeptic UlcerEsophagusEsophagoscopyGastric MucosaGastrointestinal MotilityTreatment OutcomeEndoscopy, Digestive SystemEsophagitisDigestive System Surgical ProceduresIleostomyIntestinal MucosaStomach UlcerDyspepsiaGastritisIntestine, SmallDigestive System Physiological PhenomenaIleumGastric JuiceNeoplasms, Multiple PrimaryMucous MembraneBarrett EsophagusAdministration, OralGastroesophageal RefluxHelicobacter InfectionsBiopsyAnti-Inflammatory Agents, Non-SteroidalHelicobacter pyloriLower Gastrointestinal TractDuodenal DiseasesIntestinesRetrospective StudiesProspective StudiesJejunumTime FactorsPostoperative ComplicationsColonIntestinal AbsorptionUpper ExtremityUrinary Tract InfectionsDuodenal ObstructionHematologic NeoplasmsRisk FactorsIntestine, LargeCecum