What is a primary symptom associated with a lower gastrointestinal bleed?

The primary symptom associated with a lower gastrointestinal bleed is bright red blood in the stool. This symptom indicates that the bleeding is occurring in the lower portions of the gastrointestinal tract, such as the colon or rectum. When there is bleeding from these areas, the blood usually appears fresh and bright red because it has not had a chance to be digested or altered by the digestive process, which typically occurs in the upper gastrointestinal tract.

In contrast, melena, black tarry stools, typically suggest an upper gastrointestinal bleed, as the blood has undergone digestion and has been altered by digestive enzymes, which gives it a darker appearance. Similarly, black tarry stools also indicate an upper GI source due to the digestion process affecting the color of the blood. While abdominal pain can occur in various gastrointestinal conditions, including bleeding, it is not a specific or primary indicator of lower gastrointestinal bleeding compared to the presence of bright red blood.