Melena

Melena is the passage of black, tarry stools that result from digestion of blood in the gastrointestinal tract. The stools are typically foul smelling and sticky, and their dark color arises from chemical changes to hemoglobin as blood travels through the gut (including formation of stercobilin). Melena usually indicates bleeding proximal to the ligament of Treitz, i.e., an upper gastrointestinal source, but slow, intermittent bleeding from the small intestine or a large swallowed amount of blood can also produce melena.

Differential diagnosis includes other causes of dark stools and colors produced by nonblood substances. Hematochezia refers to bright red or maroon stools and generally points to lower GI bleeding or a rapid upper GI bleed with rapid transit. Iron or bismuth preparations can also cause dark stools that resemble melena but are not due to GI blood loss.

Common causes of melena include peptic ulcers (gastric or duodenal), gastritis, esophageal or gastroduodenal varices, Mallory-Weiss tear, gastric or duodenal cancer, Dieulafoy lesion, and other upper GI lesions. NSAID use, aspirin, and H. pylori infection are important risk factors. Less commonly, bleeding from the small intestine or, rarely, swallowed maternal blood during delivery may present with melena.

Evaluation involves history, physical examination, and targeted testing. Labs often show anemia if bleeding is ongoing or chronic. Tests may include complete blood count, iron studies, coagulation profile, and stool occult blood testing. Endoscopic evaluation (esophagogastroduodenoscopy) is the primary diagnostic and therapeutic tool for suspected upper GI bleeding; imaging may be used if bleeding is not localized.

Management emphasizes stabilization and identification of the source. Initial resuscitation with intravenous access and fluids, with transfusion as needed, is followed by specific therapy for the underlying cause (e.g., proton pump inhibitors for ulcer bleeding, endoscopic hemostasis for variceal or other lesions).