What is the medical term for very dark, tarry feces or vomitus resulting from gastrointestinal secretions acting on blood?

The correct answer is melena, which refers specifically to very dark, tarry feces. This condition arises when blood in the gastrointestinal tract is broken down by digestive enzymes and bacteria, leading to the characteristic black coloration and foul smell. Melena typically indicates bleeding from the upper gastrointestinal tract, such as from a peptic ulcer or esophageal varices, where the blood has a longer transit time, allowing for the chemical breakdown that causes the tarry appearance.

The other terms relate to different medical scenarios. Hematemesis refers to vomiting blood, which is differentiated from melena as it does not pertain to fecal matter. Hematochezia indicates bright red blood in stool, suggesting lower gastrointestinal bleeding that has not been broken down. Steatorrhea describes fatty stools, which is not related to blood or its breakdown but instead indicates malabsorption of fats in the gastrointestinal system. Understanding these distinctions is crucial for identifying various gastrointestinal issues in a clinical context.