Melena

What is Melena?

Melena is the passage of black, tarry stool caused by digested blood and usually indicates an upper gastrointestinal source. The melena definition highlights that oxidized hemoglobin, which has a characteristic dark and sticky appearance, reflects digested blood. Substances such as iron, bismuth, or certain foods can also darken stool without causing melena. Melena can persist for several days even after the primary hemorrhage has stopped.

Differentiating black stools from discoloration caused by iron or diet is a critical diagnostic step. A black tarry stool usually indicates at least 50 mL of blood loss into the upper tract. Clinicians assess the bloody stool together with the patient’s hemodynamic status to determine the urgency of resuscitation.

What causes Melena?

Melena occurs when blood is digested as it passes through the upper gastrointestinal tract, such as from the esophagus, stomach, or duodenum. Less commonly, slower bleeding from the small bowel or cecum can occasionally also produce tarry feces. Common etiologies include peptic ulcer disease, erosive gastritis, and portal hypertension leading to esophageal varices. Small intestinal lesions, such as angioectasias or malignant masses, may also cause persistent oozing.

Distinguishing melena vs hematochezia helps clinicians localize the source of a GI bleed. While melena signifies an upper gastrointestinal source, hematochezia more often indicates lower gastrointestinal bleeding distal to the ligament of Treitz. In an assessment to differentiate hematochezia vs melena, brisk upper hemorrhage can occasionally present as red blood in stools if intestinal transit is rapid. Coagulopathy often magnifies minor mucosal defects into significant bleeding events.

What are the signs and symptoms associated with Melena?

Signs and symptoms of GI bleed include tachycardia, hypotension, and skin pallor. Associated melena symptoms, such as orthostatic tachycardia or weakness, signal severe intravascular volume depletion. Chronic bleeding often manifests as fatigue, iron deficiency anemia, and vague abdominal discomfort. These signs and symptoms of GI bleeding should trigger a focused physical examination to evaluate the degree of blood loss.

Variceal bleeding often occurs alongside signs of chronic liver disease, such as splenomegaly and ascites. Providers review melena-related stool changes as part of a comprehensive assessment for a GI bleed. Comparing melena vs hematochezia alongside clinical history, such as NSAID use, helps refine the suspected source. Hepatic encephalopathy (brain dysfunction from liver failure) may also develop if nitrogenous products from digested blood accumulate.

How is the cause of Melena diagnosed?

Initial diagnostic steps focus on stabilizing the individual through intravenous access and fluid resuscitation. Laboratory evaluation typically reveals a drop in hemoglobin and an elevated blood urea nitrogen (BUN) to creatinine ratio. This ratio may support an upper gastrointestinal source for black stools, though it is not diagnostic. Nasogastric aspiration or lavage may provide supportive evidence of upper GI bleeding, but it is not routinely required.

Upper endoscopy identifies lesions like ulcers or varices within 24 hours of the patient’s arrival. Capsule endoscopy or small-bowel enteroscopy explores obscure sources if the initial endoscopy remains negative despite persistent melena. CT angiography provides rapid localization for brisk hemorrhage and can guide interventional embolization.

How is Melena treated?

Primary melena treatment prioritizes airway protection and volume resuscitation with crystalloids or blood products. Clinicians generally maintain a transfusion threshold of 7 g/dL in stable cases. Proton pump inhibitor (PPI) infusions manage suspected ulcer bleeding by stabilizing clots. Vasoactive drugs and prophylactic antibiotics are essential when variceal rupture is the suspected cause.

Endoscopic hemostasis utilizing clips, thermal therapy, or injection effectively manages high-risk mucosal lesions. For variceal bleeding, treatment includes endoscopic band ligation to occlude the vessels. Chronic melena treatment depends on the cause and may include eradicating H. pylori for peptic ulcer disease and starting beta-blockers to reduce portal hypertension. When endoscopy fails to secure hemostasis, interventional radiology or surgery provides definitive care.

What are the most important facts to know about Melena?

• Melena is black, tarry stool caused by digested blood and usually indicates upper gastrointestinal bleeding.
• Common causes include peptic ulcer disease, gastritis or esophagitis, and variceal bleeding, often requiring a comparison of hematochezia vs melena for anatomical localization.
• Assessment focuses on the signs and symptoms of GI bleed, such as pallor, tachycardia, and orthostatic hypotension.
• Evaluation includes hemodynamic assessment, laboratory studies, and early upper endoscopy, while the BUN:Cr ratio may support an upper source.
• Melena treatment involves resuscitation, PPIs, endoscopic interventions, and portal pressure management.