This information is intended only to provide general guidance. It does not provide definitive medical advice. It is important that you consult your doctor about your specific condition.
Rectal bleeding is the passage of blood from the rectum and anus. The blood may be bright red, maroon-colored, or black and tarry. Occult bleeding is when there is blood in the stool that can only be discovered by a chemical test on normal-colored stool. The intestine is a hollow muscular tube that begins at the bottom of the stomach; it is divided into the small intestine, which is the upper part where nutrients are absorbed into the system, and the colon, or large intestine, where wastes are stored and fluid is removed to create a solid stool. The rectum is the lower few inches of the colon, and the anus is the valve right at the opening of the rectum to the outside. Most rectal bleeding originates in the colon, rectum, or anus.
What causes rectal bleeding?
The most common causes of rectal bleeding are hemorrhoids and anal fissures. Hemorrhoids are enlarged, irritated veins in the anus. An anal fissure is a tear in the inner lining of the anus. There is typically red blood predominantly seen on the toilet paper, although there may also be some red blood in the toilet water or on the stool. A hard stool or excessive straining may start the bleeding from a hemorrhoid or anal fissure.
Other causes of rectal bleeding include:
- Cancer of the colon or anus.
- Angiodysplasia, which is a small, abnormal cluster of blood vessels on the inner surface of the intestine.
- Ulcerative colitis or proctitis (inflammation of the rectum)
- Colon polyps: Bleeding can occur from the polyp itself or from the site of a recent polyp removal during a colonoscopy.
- Diverticulosis, which is the presence of pouches bulging out from the colon.
- Ischemic colitis: inflammation of the colon due to a shortage of blood supply.
- Ulcers of the rectum or colon.
- Infections of the colon, usually in association with diarrhea.
- Radiation colitis or proctitis, most commonly from radiation therapy for prostate or uterine cancer.
- Rectal prolapse (bulging of the rectum out through the anus).
- Meckel's diverticulum, a pouch protruding from the lower part of the small intestine; this is present since birth and commonly causes bleeding in children and younger adults.
- Sources of bleeding in the small intestine or stomach. This usually occurs when there is severe bleeding from a stomach or duodenal ulcer, and the blood is typically maroon-colored or black and tarry.
Occult bleeding, in which there is no visible bleeding, can be due to a problem anywhere in the stomach or intestine. It is usually discovered via a routine chemical test on a stool sample or when there is iron deficiency anemia suggesting blood and iron loss.
When should you see a doctor for rectal bleeding?
Any rectal bleeding needs to be evaluated by a doctor, either a gastroenterologist such as Dr. Albert M. Harary, who practices gastroenterology in New York City, or a colon/rectal surgeon (proctologist). One exception is red blood on the toilet paper that only lasts 1 or 2 days in someone under 40 years old that only occurs after hard stool or with obvious anal pain. This is most likely due to a hemorrhoid or anal fissure and does not require seeing a doctor if it does not occur frequently.
If you have any of the following, you should contact your own doctor immediately or go to emergency department:
- Black, tarry, foul-smelling stool (called melena), indicating significant hemorrhage in the stomach or small intestine (the blood changes color as is exposed to the stomach acid or passes through the intestine).
- A flow of active bleeding measuring one-quarter to one- half cup or more .
- Repeated episodes of significant bleeding throughout the day.
- Dizziness or lightheadedness when standing up.
- Cold, clammy skin or pale skin.
- Confusion or blurry vision.
- Rapid breathing.
- Moderate or severe abdominal pain.
How is the cause of rectal bleeding evaluated?
Dr. Albert M. Harary, in his New York City office, will first perform a history and physical examination. A low blood pressure or rapid heartbeat suggests that a large amount of blood has been lost and urgent care is needed. He may obtain blood tests including a complete blood count and iron levels. It is often necessary to do tests to look inside the colon to identify the bleeding source. These tests include anoscopy (in which a very short, cone-shaped tube is inserted a few inches through the anus), flexible sigmoidoscopy, colonoscopy, or various x-ray or nuclear medicine tests.
How is rectal bleeding treated?
If a large amount of blood has been lost and is causing low blood pressure or severe anemia, inpatient observation in the hospital is necessary, and a blood transfusion may sometimes need to be done. Small amounts of rectal bleeding due to hemorrhoids or anal fissures can be treated with creams or suppositories, correcting constipation (see my webpage on constipation), and avoiding excessive straining and spending too much time on the toilet. The treatment of other causes of rectal bleeding depends on identifying and correcting the cause. Aspirin and nonsteroidal anti-inflammatory drugs (NSAID’s, arthritis pain medications such as ibuprofen, naproxen, Aleve, Motrin, Advil, etc.) should be avoided unless aspirin is medically necessary because of a coronary stent, heart disease, or a previous stroke or mini-stroke (consult your doctor about this).