Black and Bloody Stools - Melena and Hematochezia
Melena - Refers to passage of black, tarry (sticky and shiny) 

stools. Occult blood tests are positive. Involves loss 

of at least 60 mL of blood into the gastrointestinal 

tract (less in children), usually from the esophagus, 

stomach, or duodenum and transit time of 7—14 

hours. Less commonly, when transit is slow, blood 

loss originates in the jejunum, ileum, or ascending 

colon. In infants, melena may result from 

swallowing blood during the birth. 

Black, Nonsticky Stools - May result from other causes, with negative occult 

blood tests. These stools have no pathologic 

significance. 

Red Blood in the Stools (hematochezia) - Usually originates in the colon, rectum, or anus; 

much less frequently from the jejunum or ileum. 

Upper gastrointestinal hemorrhage may also cause 

red stools; blood loss is then usually large (more 

than a liter). Rapid transit through the intestinal 

tract leaves insufficient time for the blood to turn 

black from oxidation of iron in hemoglobin. 


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