Gastrointestinal bleeding is diagnosed when someone has either overt or covert bleeding in the intestinal tract. 

Overt bleeding is manifested by passing blood of varying color in the stool. Depending on the source of bleeding, the color of the blood may be either fresh or dark and sometimes even black. Generally the color of the blood gives the doctor a clue regarding an upper versus lower gastrointestinal source. On most occasions, bleeding coming from the upper gastrointestinal tract, namely the esophagus, stomach or upper small bowel manifests as dark black stool also called melena. Bleeding further downstream in the small bowel and/colon manifests as bright red blood or maroon colored stool.

Covert bleeding usually manifests as a drop in blood counts (hemoglobin) or anemia. Patients may present with generalized fatigue, exertional shortness of breath or dizziness. Patients may require blood transfusion if they have significant symptomatic anemia. When the stool is tested for microscopic amounts of blood with the guaiac stool test card, it turns positive. Anemia occurs when the rate of intestinal blood loss exceeds the capacity of the bone marrow to produce new red blood cells.

Evaluation of gastrointestinal bleeding requires endoscopic procedures such as an upper gastrointestinal endoscopy and/or a colonoscopy. Based on above clinical clues, the source of intestinal bleeding may require first performing an upper endoscopy followed by a colonoscopy or vice versa. The causes of upper gastro-intestinal bleeding can be varied such as peptic ulcer disease, esophageal ulcers, esophageal varices, gastric erosions from nonsteroidal anti-inflammatory drugs, bleeding blood vessels such as arteriovenous malformations which tend to occur in the elderly. Lower gastrointestinal bleeding can occur from inflammation or ulcers occurring in the small intestine or colon from nonsteroidal anti-inflammatory drugs or inflammatory bowel disease such as ulcerative colitis/Crohn’s disease. Other causes include arteriovenous malformations, diverticulosis, and hemorrhoids.

Performing endoscopy and/or colonoscopy not only helps the gastroenterologist ascertain the cause of bleeding but also enables endoscopic treatment of active bleeding such as ulcers, varices, arteriovenous malformations.