Blood in the stool is primarily caused by bleeding somewhere along the gastrointestinal tract, states WebMD. This internal hemorrhaging can be attributed to several disorders and diseases, including hemorrhoids, diverticular disease, anal fissures, colitis, polyps and tumors, angiodysplasia, Crohn's disease and esophageal problems.
Blood in the stool may vary in coloration, which is suggestive of the location of the bleeding in the alimentary canal. Depending on the bleeding site, the color of blood in the stool can range from bright red to black and tarry, notes MedicineNet. Some likely causes of blood are typically harmless and only result in mild discomfort. However, it may also indicate a serious medical condition.
Diverticular disease is the presence of tiny pouches protruding from the intestinal wall. These projections are normally harmless but may become infected and bleed. Anal fissures refer to tiny cuts or cracks in the anal tissue lining, which occur from passing large, compact stool. Colitis is the irritation and swelling of the colon, which is linked to inflammatory bowel disease and infections. Ulcerative colitis may be accompanied by loose bowel movements, exhaustion, rectal pain and abdominal cramping, according to Mayo Clinic.
Open wounds in the stomach, called peptic ulcers, may also cause fecal blood. These sores are mainly due to a bacterial infection or to an extended use of anti-inflammatory medications, such as ibuprofen, aspirin and naproxen. Abnormal growths that are either benign or cancerous may also result in the presence of blood in the stool.