Lower gastrointestinal (GI) bleeding is a frequent cause for hospital admissions with an annual incidence of approximately 20 to 27 cases per 100,000 persons in the United States.1 Morbidity and mortality vary according to the underlying cause of the GI bleed, with reported mortality rates of 2% to 20% for lower GI bleeding and as high as 40% for hemodynamically unstable patients.2 Lower GI bleeding is defined as bleeding that occurs distal to the ligament of Treitz, with upper GI bleeding occurring proximally. Clinical presentations vary based on the source of the bleed and cause; however, acute lower GI bleeds typically present with hematochezia, noting that secondary to the cathartic effects of blood, a brisk upper GI bleed may present in a similar manner.3 Causes of lower GI bleeding may be anatomic, such as diverticulosis (33.5%); vascular, such as hemorrhoids (22.5%), angioectasia, or ischemia; neoplastic (12.7%); inflammatory as with inflammatory bowel disease; or infectious.4 If the workup of the large bowel is negative, then patients are suspected of having a small bowel bleed. There are several classification schemes used to describe lower GI bleeding related to the duration and severity of the bleed as well as the results of upper and lower endoscopy/imaging. When correlating with the amount of bleeding, lower GI bleeds can be categorized as massive, moderate, or occult. Massive bleeding is defined by the passage of profuse hematochezia with hemodynamic instability. Moderate bleeding reflects hematochezia in hemodynamically stable patients. Occult bleeding refers to the presence of a positive fecal-occult blood test or iron deficiency anemia without another identifiable source and without frank hematochezia.5 Obscure bleeding refers to patients who have recurrent bleeding after negative endoscopic evaluation and advanced radiologic assessment of the small bowel and can be either acute or occult.

WORKUP RECOMMENDATIONS FOR ACUTE LOWER GASTROINTESTINAL BLEEDING

The workup of patients presenting with acute lower GI bleeding involves resuscitation, localizing the site of bleeding, and intervention to stop the source of the bleeding, as appropriate. The main tools of the workup include direct visualization with proctoscopy/colonoscopy and imaging with computed tomography angiography (CTA), nuclear scintigraphy, or angiography. Although surgery was once a necessity for patients with ongoing lower GI bleed, advanced techniques in endoscopy and angiography have improved detection and treatment, with surgery now reserved for cases in which more conservative management has failed.6 The clinical presentation of patients during the triaging process as well as the services available at a hospital dictate the order and priority in which tests are used in the workup of an active lower GI bleed.1 Any patient with hemodynamic instability must first be resuscitated. If endoscopy is available, it is generally the first test preformed; however, there are significant limitations. The colon must first be prepped in order to clear enteric contents and blood, which could obscure the source of bleeding. Even rapid bowel preparations take at least several hours, which may not be possible in patients with ongoing bleeding. Additionally, in some series, colonoscopy detects the source of bleeding in only 13% to 40%.2 In cases whereby emergent endoscopy is not indicated, patients will typically be sent for an imaging study, such as CTA, nuclear scintigraphy, or catheter angiography, depending on the local availability and clinical expertise. In patients who are clinically stable at presentation, more conservative management is generally indicated, with many patients being worked up with elective endoscopy.