[Lower gastrointestinal bleeding: the great unknown]

Lower gastrointestinal bleeding represents one-fourth of all gastrointestinal hemorrhages. The bleeding usually originates in the colon while less than 10% of cases originate in the small bowel. Colonoscopy is considered the initial procedure of choice due to its diagnostic efficacy, safety, and therapeutic potential. Mesenteric arteriography can be an alternative in patients with massive hemorrhage. Helical computed tomography of the abdomen with endovenous contrast can be useful but has not been directly compared with arteriography. When the results of gastroscopy and colonoscopy are negative, small bowel bleeding is suspected. Capsule endoscopy allows non-invasive examination of the entire small bowel. The diagnostic efficacy of this procedure is clearly superior to that of other conventional examinations and, compared with intraoperative endoscopy, capsule endoscopy has a sensitivity of 95% and a specificity of 75%. Double balloon enteroscopy is a new modality that also allows complete examination of the small bowel with the additional advantage of its therapeutic potential. Definitive diagnosis of the hemorrhagic site is essential for appropriate treatment. Endoscopic and angiographic advances are therapeutic alternatives to surgical resection. Endoscopic treatment is indicated in lesions with active bleeding or signs of recent hemorrhage. Arterial embolization can be a therapeutic alternative when arteriography shows active hemorrhage. Surgical treatment is reserved for patients with persistent bleeding in whom other options have failed.