What is melena characterized by?

Melena is characterized by the presence of black tarry stool, which indicates that there is digested blood in the gastrointestinal tract. This coloration occurs due to the breakdown of hemoglobin in the blood as it passes through the intestines, often as a result of bleeding from areas higher in the digestive tract, such as the stomach or esophagus. The tarry appearance reflects the degree of digestion that the blood has undergone, making it a significant indicator for clinicians to consider potential sources of internal bleeding.

Bright red blood in the stool is typically associated with hematochezia, which indicates a lower gastrointestinal bleed. Liquid diarrhea refers to loose stools not necessarily related to the presence of blood. Pale-colored stool can suggest conditions related to bile duct obstruction or liver dysfunction but is not characteristic of melena. Understanding these distinctions is crucial for recognizing the implications of different stool characteristics in clinical assessments.