Melena is defined as:

Melena refers specifically to the presence of black, tarry, sticky stools, which is indicative of gastrointestinal bleeding that has occurred higher up in the digestive tract, such as the esophagus, stomach, or duodenum. The dark color is a result of the blood being digested as it passes through the intestines, which changes its color due to the action of digestive enzymes and gut bacteria. This characteristic appearance is a crucial symptom that healthcare providers assess in order to determine the presence and location of possible bleeding, which is essential for diagnosis and treatment. Understanding melena helps in recognizing serious health issues and the need for prompt medical attention.