Gastrointestinal (GI) bleeding is the loss of blood from anywhere along the gastrointestinal tract from mouth to anus. Any bleeding source proximal to the ligament of Treitz is classified as an upper GI bleed, whereas any bleeding source distal to the ligament of Treitz is considered a lower GI bleed.

The degree of GI bleed can vary considerably. Some patients will present with an anemia of insidious onset from slow GI blood loss, while others will present with hypovolemic shock from acute blood loss anemia due to a more brisk bleeding source. The symptoms can range from asymptomatic to overt melena or hematochezia, indicating more rapid blood loss per rectum through the GI tract.

In all settings of a suspected GI bleed, orthostatic vital signs should be checked in addition to routine vitals, as orthostatics can detect hypovolemia that routine vitals may not suggest.

Upper GI Bleeding:
Patients with upper GI bleeding will often present with melena, a marker of digested red blood cells passing in the stool. Blood is a laxative, and it is not uncommon for these patients to present with frequent bowel movements. The sources of upper GI bleeds are innumerable; peptic ulcer disease, malignancy, varices, esophagitis, gastritis, duodenitis, and angiodysplasias are among the more common etiologies.

Depending on the severity of the GI bleed and the proximity to the stomach, patients can present with hematemesis as well. In the setting of brisk upper GI bleeds, patients can present with bright red blood per rectum or hematochezia.

Active upper GI bleeding is a medical emergency that warrants attentive in-hospital management. Esophagogastroduodenoscopy (EGD) should ideally be performed within 24 hours in an attempt to identify and control the source of bleeding.

Lower GI Bleeding:
Lower GI bleeds will present most commonly with hematochezia or bright red blood per rectum; rarely, patients will present with melena. However, some lower GI bleeding sources (ie, malignancy) present with chronic microscopic bleeding, and patients often present with symptomatic anemia. Similar to an upper GI bleed, there are many sources of lower GI bleeding, with diverticula, malignancy, hemorrhoids, fissures, angiectasias, ischemia, infectious or inflammatory colitis, and polyps among the more common etiologies. Young children can often present with lower GI bleeding from allergic colitis, necrotizing enterocolitis, or fissures. Colonic arterial fistulas due to foreign bodies, eg, toothpicks, can be a cause of bleeding.

In the presence of hemodynamic instability, hypovolemia, and orthostatic hypotension, lower GI bleeding should be considered life-threatening and given prompt emergency attention.

Management requires immediate emergency intervention for rapid blood loss, including resuscitation, intravenous (IV) fluids, and blood transfusions.

In the setting of acute, hemodynamically compromising bleeding from either an upper or a lower GI source, initial efforts should be made to emergently volume resuscitate patients and to start antacid blockers (proton pump inhibitors) if an upper GI source is suspected. With the exception of bleeding esophageal varices, which warrant endoscopic evaluation within 12 hours, endoscopy should be performed ideally within 24 hours for both diagnostic and therapeutic purposes. Interventional radiology via embolization and surgery also offer potential interventions to stop GI bleeding.