Lower GI bleeding is a very broad topic, which can encompass situations from a small amount of red blood on tissue paper associated with formed brown stool, to life-threatening severe haemorrhage. Much of the literature on this topic focuses on acute bleeding necessitating hospitalisation and urgent intervention. The literature that is available focuses primarily on medical intervention and support, which will be covered in another review in this series. Causes for lower GI bleeding include diverticular disease, vascular ectasia, ischemic, inflammatory or infectious colitis, colonic neoplasia (including post polypectomy bleeding), anorectal causes (including haemorrhoids, fissures and rectal varices), and small bowel lesions (Crohn's, vascular ectasia, Meckel's diverticula, and small bowel tumours). Different clinical series identified these lesions in varying frequencies. Factors associated with the development of acute lower GI bleeding include advanced age and use of non-steroidal anti-inflammatory medication. Colonoscopy is the single most frequent intervention in evaluating all the patients with lower GI bleeding. Determining the precise impact of colonoscopy on the outcome of lower GI bleeding is difficult due to the retrospective nature of many studies, and the frequent inability to definitively establish the exact bleeding site.