Identifying the cause of gastrointestinal bleeding.
D000208:Acute Disease; D004381:Duodenal Ulcer / Q000150:complications; D004945:Esophagoscopy; D005336:Fiber Optic Technology; D006471:Gastrointestinal Hemorrhage / Q000175:diagnosis* / Q000209:etiology*; D005773:Gastroscopy; D006801:Humans; D013997:Time Factors