Dr. Abhishek Shukla explained that gastrointestinal bleeding can broadly present in two forms – black stool (melena) or red blood in stool (hematochezia). Black stool occurs when blood has been partially digested while passing through the upper gastrointestinal tract, most commonly due to ulcers, gastritis, or esophageal varices. This digested blood gives the stool its characteristic tarry black appearance, a condition known as melena. In such cases, an upper GI endoscopy is essential to identif