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Lower GI bleeding is defined as the loss of blood from the GI tract distal to the ligament of Treitz. Like upper GI bleeding, lower GI bleeding is a common problem in emergency medicine and should be considered potentially life-threatening until proven otherwise.

Lower GI bleeding occurs less often than upper GI bleeding, with an annual incidence of approximately 20 per 100,000. Because of this, upper GI bleeds are the most common source for all causes of blood detected in the lower GI system, as blood must travel through the upper GI tract down to the lower GI system. Among patients with an established lower GI source of bleeding (i.e., bleeding past the ligament of Treitz), the most common etiology is diverticular disease, followed by colitis, adenomatous polyps, and malignancies.1,2 Lower GI bleeding is more common among males and increases significantly in the elderly.3

It is estimated that 80% of lower GI bleeding will resolve spontaneously.4 However, recommendations predicting which patients will have spontaneous resolution of bleeding and not be at risk for complications have yet to be established. This is partly due to the difficulty in establishing a diagnosis. In one study, a cause for bleeding was found in <50% of the cases.5

However, as with any emergency, the medical history, physical examination, and diagnostics often must be accomplished simultaneously with resuscitation and stabilization. Factors associated with a high morbidity rate are hemodynamic instability, repeated hematochezia, gross blood on initial rectal examination, initial hematocrit <35%, syncope, non-tender abdomen, aspirin use, and more than two comorbid conditions.1,2,6

Hematochezia is defined as either bright red or maroon-colored bleeding that comes from the rectum. Historically, hematochezia represents bleeding from a lower GI source. However hematochezia may come from an upper GI source, usually indicating brisk bleeding. This may be accompanied by hematemesis and is usually associated with hemodynamic instability. Approximately 10% of hematochezia may be associated with upper GI bleeding.7 Melena represents dark or black-colored stools and usually represents bleeding from an upper GI source (proximal to the ligament of Treitz) but may also represent bleeding from a lower GI source due to slow bleeding.


Diverticular bleeding is usually painless and is thought to result from erosion into the penetrating artery of the diverticulum. Diverticular bleeding may be massive, but up to 90% of episodes will resolve spontaneously. Recurrence of bleeding, however, can occur in up to half of patients with diverticular bleeding.8,9 Although most diverticula are located on the left colon, the right-sided diverticula are thought to be more likely to bleed.10 Elderly patients with underlying medical illnesses, those with increased needs for transfusion, and those taking anticoagulants or NSAIDs have increased rates of morbidity and mortality.8

Vascular Ectasia

Vascular ectasia, including arteriovenous malformations and angiodysplasias, is a common cause of lower GI bleeding, especially right-sided colonic lesions. Vascular ectasia ...

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