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Etiology of lower gastrointestinal bleeding in adults

Lisa Strate, MD, MPH
Section Editor
J Thomas Lamont, MD
Deputy Editor
Shilpa Grover, MD, MPH, AGAF


Lower gastrointestinal bleeding (LGIB) refers to blood loss of recent onset originating from a site distal to the ligament of Treitz [1]. It is usually suspected when patients complain of hematochezia (passage of maroon or bright red blood or blood clots per rectum). This is different from the clinical presentation of upper gastrointestinal (GI) bleeding, which includes hematemesis (vomiting of blood or coffee-ground-like material) and/or melena (black, tarry stools). Although helpful, the distinctions based upon stool color are not absolute since melena can be seen with GI bleeding from the right colon (or small intestine), and hematochezia can be seen with massive upper GI bleeding [2-4]. Therefore, it is imperative to exclude a massive upper GI bleed in hemodynamically unstable patients presenting with hematochezia [5]. A nasogastric tube lavage that yields blood or coffee-ground-like material confirms the diagnosis of upper GI bleeding; however, lavage may not be positive if bleeding has ceased or arises beyond a closed pylorus. (See "Approach to acute upper gastrointestinal bleeding in adults".)

The epidemiology of GI bleeding appears to be changing. Studies indicate that the incidence of hospitalizations for LGIB is similar to that of upper GI bleeding, largely due to a decrease in upper GI events [6,7].

This topic review will focus on the major causes of LGIB originating from the colon and briefly summarize the management of some of these disorders. Although the definition of LGIB includes small bowel sources, the clinical presentation, management, and outcomes of small bowel bleeding are generally distinct from bleeding from colon sources [8]. The diagnostic approach to patients with LGIB, suspected small bowel bleeding, and occult gastrointestinal bleeding are discussed separately. (See "Approach to acute lower gastrointestinal bleeding in adults" and "Evaluation of occult gastrointestinal bleeding" and "Evaluation of suspected small bowel bleeding (formerly obscure gastrointestinal bleeding)".)


The causes of lower gastrointestinal bleeding (LGIB) may be grouped into several categories (table 1):

Anatomic (diverticulosis)

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Literature review current through: Oct 2017. | This topic last updated: Sep 05, 2017.
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