Arteriovenous malformation, including angiodysplasia (a common cause of bleeding in the elderly).

Meckel's diverticulum (usually causes acute lower GI bleeding in children but can present in young adults).

Right colon diverticulosis (more common in non-Western countries, where the diverticula are predominantly left sided).

Inflammatory bowel disease (Crohn's disease).

Haemobilia (bleeding from the biliary tree usually occurs after instrumentation (e.g. ERCP), surgery (cholecystectomy) or trauma. It may be associated with jaundice and biliary colic).

Haemosuccus pancreaticus (bleeding from the pancreatic duct).

Aorto-enteric fistula (fistula between aneurysmal aorta or aortic graft and the gut, most often duodenum).

Ectopic varices (usually but not invariable associated with upper GI tract varices; ectopic varices can be difficult to detect especially if not considered to be a cause of bleeding).