Rectal bleeding is any blood that passes from the anus that can show up in the stool or dripping into the toilet bowl. The blood can range in color from bright red to a dark tar-like color. Bleeding can occur from a variety of acute or chronic conditions. People should seek immediate medical attention if the bleeding is heavy and accompanied by abdominal pain. A physician should be contacted if rectal bleeding lasts for more than a day or two and is not caused by an obvious cause such as constipation.