Melena
Formal Definition
Black, tarry, foul-smelling stool resulting from upper gastrointestinal bleeding (proximal to the ligament of Treitz), where hemoglobin is oxidized to hematin by intestinal bacteria and digestive enzymes during transit; typically requires ≥50–100 mL of blood loss.
How It's Used on the Ward
"Melenic stools" or "melanotic stool" or just "melena" — a cardinal sign of upper GI bleed; "black tarry stool" is how it's described to non-medical staff.
Example
""Woke up with black tarry stools — smell is distinctive, testing guaiac positive, hemoglobin dropped 2.4 points overnight. Upper GI bleed until proven otherwise. Type and crossmatch, two large-bore IVs, NPO, GI aware for urgent scope.""
Clinical Context
Differentiate from iron or bismuth (Pepto-Bismol) — these cause black stool but guaiac negative. Melena origin: esophagus, stomach, duodenum (most common: peptic ulcer, esophageal varices, Mallory-Weiss tear, gastric cancer). Hematochezia (bright red blood per rectum) = lower GI source OR massive upper GI bleed with rapid transit. Initial resuscitation: 2 large-bore peripheral IVs, type and crossmatch, NPO, IV PPI, octreotide if variceal bleed suspected, early GI consult.
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