Acute lower gastrointestinal (GI) bleeding includes a wide clinical spectrum, ranging from minute bleeding to massive haemorrhage with haemodynamic instability. Lower GI bleeding is approximately one fifth as common as upper GI bleeding and accounts for approximately 20 to 30 hospitalisations per 100,000 adults per year.[1]Rockey DC. Lower gastrointestinal bleeding. Gastroenterology. 2006;130:165-171.
http://www.ncbi.nlm.nih.gov/pubmed/16401479?tool=bestpractice.com
[2]Longstreth GF. Epidemiology and outcome of patients hospitalized with acute lower gastrointestinal hemorrhage: a population-based study. Am J Gastroenterol. 1997;92:419-424.
http://www.ncbi.nlm.nih.gov/pubmed/9068461?tool=bestpractice.com
The incidence of lower GI bleeding increases with age.
In developed countries, the two most common causes of acute lower GI bleeding, resulting in significant blood loss, are colonic diverticular disease and angiodysplasia. Patients with severe bleeding or significant comorbid states require rapid identification and aggressive resuscitation. Haemodynamically insignificant bleeding may frequently result from haemorrhoids and colonic neoplasms. Rare causes of bleeding include solitary rectal ulcer, vasculitis, and endometriosis. Fifteen percent (15%) of patients who present with lower GI bleeding have an upper GI source following investigation.[3]Strate LL, Gralnek IM. ACG Clinical Guideline: Management of Patients With Acute Lower Gastrointestinal Bleeding. Am J Gastroenterol. 2016 May;111(5):755.
https://www.doi.org/10.1038/ajg.2016.155
http://www.ncbi.nlm.nih.gov/pubmed/27151132?tool=bestpractice.com
Colonoscopy is the mainstay of the evaluation in patients in whom anorectal or upper GI causes have been ruled out. This is performed to localise the bleeding source and to enable haemostasis. Endoscopic haemostasis is successful in most cases. Mesenteric angiography or nuclear imaging is only performed in patients in whom colonoscopy is not feasible or where there is persistent bleeding and a negative colonoscopy. The source of bleeding cannot be definitively identified in up to 25% of patients.[1]Rockey DC. Lower gastrointestinal bleeding. Gastroenterology. 2006;130:165-171.
http://www.ncbi.nlm.nih.gov/pubmed/16401479?tool=bestpractice.com
[4]Schmulewitz N, Fisher DA, Rockey DC. Early colonoscopy for acute lower GI bleeding predicts shorter hospital stay: a retrospective study of experience in a single center. Gastrointest Endosc. 2003;58:841-846.
http://www.ncbi.nlm.nih.gov/pubmed/14652550?tool=bestpractice.com