The digestive system is made up of a series of tissues that mechanically and chemically digest food and absorb nutrients into the body to sustain life. The length of the digestive system is lined with membranes that contain specialized digestive cells, connective tissue and a rich supply of blood vessels. Diseases or damage to parts of the digestive system can cause blood to mix with the digesting food, leading to the development of bloody tissue in the stool.
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Patients may develop bloody tissue in the stool due to peptic ulcers. The stomach contains strong acids that help to break down proteins and other nutrients in food, and the lining of the stomach is protected from that acid by a thick layer of mucus. Peptic ulcers occur due to infection by the bacterium H. pylori, which infects the stomach lining and causes defects in the protective mucous layer, according to the National Digestive Diseases Information Clearinghouse. As a result, patients with peptic ulcers experience bleeding in the stomach, which leads to bloody tissue in the stool. Blood in the stool due to peptic ulcers remains in the digestive system long enough for bacteria within the intestines to digest the blood, and patients with these ulcers typically pass black, tarry and foul-smelling stools containing digested blood tissue. Peptic ulcers may be treated with antibiotics to kill the infectious bacteria and allow the stomach lining to heal.
Another possible cause of bloody tissue in the stool is Crohn's disease, an immune system disease that affects the colon and bowel. Patients with Crohn's suffer from an overactive immune system that causes lesions within the bowel. Inflammation around a lesion causes the release of chemicals called cytokines, which cause further inflammation, in a cycle that eventually leads to painful lesions throughout the colon. MayoClinic.com indicates that patients with Crohn's disease often suffer from diarrhea, ulcers, abdominal pain and weight loss, in addition to the presence of red, bloody tissue within the stool. Crohn's can be controlled with medication and lifestyle changes to increase the quality of life for the patient.
Colon cancer may also cause bleeding and the presence of bloody tissue in the stool. Colon cancer arises from specialized cells within the lining of the colon that begin to grow out of control. As the cancer progresses, colon cancer cells begin to grow into the lumen, or hollow space in the center of the colon. In addition, the cancer cells begin to harm healthy colon tissue around the tumor, causing blood to leak into the colon and leading to bloody tissue in the stool. MedlinePlus indicates that other symptoms of colon cancer include abdominal pain, abnormally narrow stools, intestinal obstructions and unexplained weight loss. Patients with these symptoms must seek immediate medical attention to address the possibility of colon cancer, since early detection improves patient prognosis.