Causes of blood in a bowel movement include hemorrhoids, an anal fissure, an anal abscess, diverticulitis and inflammatory bowel disease, according to Cleveland Clinic. The color of the blood helps determine where the blood is coming from, helping to diagnose the condition. For example, bright red blood means that the blood is coming from the rectum or the lower part of the colon and is typically due to hemorrhoids.
Hemorrhoids occur when veins in the rectum or the anus swell as a result of constipation, pregnancy, heavy lifting, anal intercourse or other factors, notes Cleveland Clinic. Treatment of the condition addresses its cause, and surgical treatment is sometimes necessary, in which doctors try to shrink or remove the hemorrhoids. Anal fissures occur when the lining in the anus tears, leading to pain and bleeding after bowel movements. Hard stools typically cause anal fissures, and they improve on their own over time. Doctors treat the condition if it does not go away on its own by prescribing ointments or medications to alleviate pain, and they perform surgery in rare cases.
An anal abscess occurs when the glands in the anus become infected, leading to a blockage and pus that requires draining, explains Cleveland Clinic. Some anal abscesses develop into anal fistulas, which doctors treat with surgery. Diverticulitis occurs when the diverticuli in the colon become blocked and infected, leading to fever and abdominal pain. Diet, antibiotics and surgery treat this condition. Inflammatory bowel disease occurs when the small or large intestine becomes inflamed, which leads to symptoms such as diarrhea, fever, rectal bleeding and intestinal blockage. There are many types of inflammatory bowel disease, and each has different treatment plans.