An elderly gentlmean, with background history of type 2 diabetes mellitus, hypertension, parkinson disease, hypercholesterolaemia, non alcohol fatty liver disease, was admiited due to 2 days history of malaena, general unwell, fatugue, and reduced in appetite. His long list of medication did included aspirin 75mg, with no other anti-coagulation or anti-platelet. Blood test showed that patient had microcytic anaemia (Hb was 8.0, comparing to 11.5 3 months ago, a significant drop). Patient was haemodynamically stable on admission. He was treated with intravenous proton pump inhibitor infusion, for his stable upper gastrointestinal bleed. Gastroscopy was performed, showed a normal result, up to second part of duodenum. Patient had colonoscopy subsequently, also showed a normal large bowel. What should be we do next to further investigate the cause of his malaena ??