Blood in the stool means there is bleeding somewhere in your digestive tract. Sometimes the amount of blood is so small that it can only be detected by a fecal occult test (which checks for hidden blood in the stool). At other times it may visible on toilet tissue or in the toilet after a bowel movement as bright red blood. Bleeding that happens higher up in the digestive tract may make stool appear black and tarry.
Possible causes of blood in stool include:
- Diverticular disease. Diverticula are small pouches that project from the colon wall. Usually diverticula don’t cause problems, but sometimes they can bleed or become infected.
- Anal fissure. A small cut or tear in the tissue lining the anus similar to the cracks that occur in chapped lips or a paper cut. Fissures are often caused by passing a large, hard stool and can be painful.
- Colitis. Inflammation of the colon. Among the more common causes are infections or inflammatory bowel disease.
- Angiodysplasia. A condition in which fragile, abnormal blood vessels lead to bleeding.
- Peptic ulcers. An open sore in the lining of the stomach or duodenum, the upper end of the small intestine. Many peptic ulcers are caused by infection with a bacterium called Helicobacter pylori (H. pylori). Long-term use or high doses of anti-inflammatory drugs such as aspirin, ibuprofen, and naproxen can also cause ulcers.
- Polyps or cancer. Polyps are benign growths that can grow, bleed, and become cancerous. Colorectal cancer is the fourth most common cancer in the U.S. It often causes bleeding that is not noticeable with the naked eye.
- Esophageal problems. Varicose veins of the esophagus or tears in the esophagus can lead to severe blood loss.