In clinical terms, the upper gastrointestinal tract refers to the digestive system above the ligament of Treitz, primarily including the duodenum, stomach, and esophagus. If there is a minor amount of bleeding in the upper gastrointestinal tract, the color of the stool may not change significantly. However, if there is substantial bleeding, the blood can react with gastric acid and may form black, tar-like stools. If gastrointestinal bleeding is detected, it is essential to seek medical attention promptly. An endoscopic examination can be performed to establish a clear diagnosis and undertake aggressive treatment, which can potentially save the patient's life.