How do you differentiate between upper and lower GI bleeding?

Differentiating between upper and lower gastrointestinal (GI) bleeding is primarily based on the characteristics of the blood observed in the stool or vomit. When blood is bright red, this typically indicates that the source of the bleeding is from the upper GI tract, such as the esophagus, stomach, or duodenum. This bright blood is usually due to more recent bleeding, as it has not had time to undergo significant changes. Conversely, dark blood, which can appear as maroon or black (also known as melena), usually indicates that the source is from the lower GI tract, such as the colon, or it can be older blood that has been digested. The presence of darker blood signifies that it has been in the gastrointestinal tract longer than fresh, bright red blood, allowing time for chemical changes to occur.

While other factors, such as the patient’s age and medical history, abdominal pain, or signs of infection, may provide additional information, they are not definitive indicators for distinguishing between upper and lower GI bleeding. The color of the blood is the most direct and observable characteristic that guides clinicians in making this critical distinction.