Lower gastrointestinal bleeding.

Lower gastrointestinal bleeding is defined as blood loss that originates from a source distal to the ligament of Treitz and results in hemodynamic instability or symptomatic anemia. Although approximately 10% to 15% of patients presenting with acute severe hematochezia have an upper gastrointestinal source of bleeding identified on upper endoscopy, the most common causes of lower gastrointestinal bleeding are diverticulosis, hemorrhoids, ischemic colitis, and angiodysplasia. As with upper gastrointestinal bleeding, lower gastrointestinal bleeding ceases spontaneously in most cases.