The causes of dark stools include certain medications, certain foods and bleeding in the upper portion of the digestive system, including the esophagus, according to Healthline. Less frequently, severe circulation problems in the digestive system may lead to dark stools.
Ulcers and other kinds of irritation may cause bleeding in the gastrointestinal tract, leading blood to mix with digestive fluids, as Healthline explains. Medications that contain bismuth and iron supplements may darken bowel movements. Dark-colored foods, including that dark chocolate cookies, black licorice and blueberries can cause tarry stools.
In rare occasions, varices, protrusions of veins in the intestines and vascular malformation may lead to dark stools, according to Healthline. Bowel ischemia, a condition in which there is a low supply of blood to the intestines, may also lead to black-colored stools. Obstructions in the digestive tract may also give rise to the condition.
Treatments for dark stools depend on the cause of the problem, and they include using stool softeners or sitz baths to reduce bleeding; taking immunosuppressants and antibiotics to counter infections and inflammatory bowel disease; and antacids to cure bleeding ulcers, according to Healthline. Surgery may aid in treating persistent bleeding, which may lead to anemia if left untreated. After surgery, a blood transfusion may help restore red blood cell count back to normal. Chemotherapy and radio therapy may help reverse dark stools that result from cancer.