Melena is defined as which of the following?

• A. Bright red blood in stool
• B. Black, tar-like feces
• C. Pale, clay-colored stool
• D. Maroon vomit

Answer: (B)

Melena is the passage of black, tar-like stool. This dark color comes from blood that has been digested as it moves through the GI tract, usually due to an upper GI source such as a peptic ulcer or gastritis. The digestion of blood by stomach acids and intestinal bacteria changes its color, so melena points to bleeding higher up in the tract rather than from the lower intestines. This is different from bright red blood in stool, which suggests a lower GI bleed or a brisk upper GI bleed, and from pale, clay-colored stool, which indicates a lack of bile. A maroon vomit would signify recent blood in the stomach or esophagus, not the stool.