Bleeding from the rectum is always indicative of a medical problem--sometimes minor, sometimes serious. The amount of blood is not a reliable indicator as to whether the condition is serious. Some rectal bleeding is invisible to the naked eye and found only by a diagnostic test. A medical professional should evaluate all rectal bleeding of an unknown origin.
Injury
Some cases of rectal bleeding can be blamed on injury. Common causes include anal intercourse, insertion of foreign objects into the rectum, severe constipation and large, firm stools that can tear the anus. An injury to the large intestine such as a stabbing, a gunshot or a car accident can also cause bleeding from the rectum.
Hemorrhoids
Both internal and external hemorrhoids--distended veins in the anal area--can cause rectal bleeding. Pregnant women, obese individuals, weightlifters, elderly individuals and people who lift or strain at work are at increased risk of hemorrhoid problems. Most episodes involve minor, intermittent bleeding, but some cases are severe enough to require urgent medical attention.
Cancer and Polyps
Rectal bleeding can be due to colon cancer, rectal cancer, or anal cancer. Accompanying symptoms may include abdominal pain, constipation, fatigue or the feeling that the rectum is not empty following a bowel movement. A benign polyp may bleed as well, especially if it grows to a large size, explains Jackson Siegelbaum Gastroenterology. These conditions become more common with age.
Endometriosis
The Merck Manual relates that endometriosis in the large intestine can cause rectal bleeding. This growth of endometrial tissue attached to the intestine bleeds during menstruation. Nausea and a loss of appetite may also be present.
Ulcerative Colitis
One symptom of ulcerative colitis is blood in the stool. This inflammatory bowel disorder affects the inner lining of the large intestine and rectum, causing sores or ulcerations that can slough tissue and bleed. Ulcerative colitis often affects people in their twenties, but can strike at any age.
Diverticulosis
Diverticulosis is a common condition in which small pouches are present in the intestine. Occasionally, a vein in one of the pouches can burst and bleed, causing bleeding from the rectum. It is more common in older people.
Infection, Food Poisoning and Infestation
Occasionally, rectal bleeding is found to be due to an intestinal infection. Food poisoning can also produce rectal bleeding along with vomiting, severe abdominal cramping and diarrhea. Tapeworm infestation is responsible for some cases, and is more common in children.
