Inclusion Criteria:  Age ≥ 18 years  New onset of acute gastrointestinal bleeding defined as:  The presence of melena/maroon stool on physical exam OR history of melena/maroon stool within 48 hours of emergency room presentation PLUS Hemoglobin drop of ≥ 20 g/L from patient's baseline Have capacity to consent Hemodynamically stable (i.e. blood pressure >100/60 or pulse <110 at the time of consent) Initial gastroscopy negative for active bleeding or potential bleeding source  Exclusion Criteria:  Inability to provide consent due to lack of capacity, language barrier or other reasons Pregnant women Prior history of small bowel surgery Prior history of Crohn's disease Prior history of small bowel or colonic strictures Prior history of abdominal radiation