Hemorrhoids, anal fissures, diverticulosis and colon polyps are the most common causes of blood in the stool, as confirmed by MedicineNet. Blood in the stool ranges in color from bright red to black.
Hemorrhoids are clumps of tissue and blood vessels within the anal canal that cause mild bleeding when enlarged, as stated by MedicineNet. An anal fissure refers to a painful tear in the anal canal that results from forced bowel movements or constipation. Anal fissure patients may have painful bowel movements, and the blood in the stool is generally mild and bright red in color. In diverticulosis, the colon contains small sacks known as diverticula. These sacks cause no problems unless they rupture and become infected, in which case the condition is known as diverticulitis. Bleeding may be moderate to severe and can be bright red, dark red, maroon or black in color.
Colon polyps are benign tumors that grow on the wall of the large intestine, according to MedicineNet. While polyps that affect the sigmoid colon sometimes cause mild, intermittent rectal bleeding that is bright red in color, polyps in the right colon tend to cause occult bleeding. Individuals who are experiencing blood in the stool need to make an appointment with a doctor for diagnosis and treatment options.