Upper gastrointestinal haemorrhage is classically bleeding from above the ligament of Trietz (the suspensory muscle of duodenum that connects to the diaphragm), can is characterised by haemetemesis and melaena.
Lower gastrointestinal haemorrhage is classically bleeding from below the ligament of Trietz (the suspensory muscle of duodenum that connects to the diaphragm), and is characterised by hematochezia (blood passed in or with the stools) or rectorrhagia (blood leaking from the rectum). Massive upper GI bleeding may also present with hematochezia.