A stool sample that appears black and tarry (melena) is typically indicative of bleeding from which site?
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Correct answer: Proximal to the ligament of Treitz
Melena results from the oxidation of iron in hemoglobin to hematin as it passes through the GI tract. This process requires several hours and contact with stomach acid and enzymes, typically localizing the bleed to the esophagus, stomach, or duodenum.
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