Digestive Tract: Rectal and Colon Diseases and Conditions


Many Americans have difficulty moving their bowels. Many things contribute to this problem, including diet and activity level. Other causes are unknown.

This article will describe some of the more common bowel problems.

Anatomy and physiology

The large bowel consists of the colon (5 feet long) and the rectum (8 inches long). (Many times the rectum is referred to as the opening where stool emerges, but that is actually the anus.) The rectum is just upstream from the anus, and the large bowel is connected to the small bowel.

Anatomy of the large bowel (colon).

The colon's main function is to process the 3 pints of liquid stool it receives each day into a manageable amount of solid stool, ready for elimination. The rectum coordinates this process. Normally, a person can pass up to 200 grams of solid stool daily. However, there is a lot of variation in the amount of stool a healthy person passes, and can vary from 3 times a day to 3 times per week.

Functional disorders

Functional disorders are conditions in which the bowel looks normal but doesn't work properly. These are the most common problems affecting the colon and rectum. The direct cause is frequently unknown.


Constipation is defined as small, hard, difficult, or infrequent stools. Constipation may be caused by:

  • Inadequate "roughage" or fiber in the diet
  • Not drinking enough fluids
  • Poor habits, especially delaying using the toilet
  • Movement problems in the large bowel, including slow or uncoordinated movement

A person who is constipated may strain during a bowel movement, or just pass very hard stool. Passage of hard stool may lead to anal problems such as fissures (painful cracks in the anal tissue lining) or hemorrhoids.

Irritable bowel syndrome (sensitive colon; spastic colon)

Irritable or sensitive bowel is a condition in which the colon muscle contracts (tightens) in an abnormal fashion, which may lead to several problems. Some patients have diarrhea, others have constipation, and others alternate between constipation and diarrhea. The abnormal contraction can lead to high pressure that builds up in the colon, causing abdominal cramps, gas, bloating, and sometimes extreme urgency (need to go the bathroom).

Treatment includes avoiding foods that make the problems worse, tailoring diet to the particular symptoms, managing stress, and medications.

Structural disorders

Structural disorders are those in which there is something abnormal that may need to be removed, altered, or repaired by an operation. These may include removing a portion of the colon for diverticulitis or for a cancer.

Anal disorders

Internal hemorrhoids

Internal hemorrhoids are normal blood vessels that line the inside of the anal opening. We are born with them. They are thought to be the fine-tuning mechanism that allows us to contain gas and avoid passing it until we it is socially acceptable. When internal hemorrhoids become enlarged as a result of straining or pregnancy, they may become irritated and start to bleed. Occasionally, internal hemorrhoids can become large enough to bulge outside the anal opening.

Hemorrhoids are swollen and inflamed veins around the anus or the lower rectum.

Traditional care for internal hemorrhoids has included improving bowel habits, using elastic bands to pull the hemorrhoids back into the rectum, or removing them surgically. Devices that use sound waves can discover exactly where the excessive blood flow is occurring into these vessels and allow the doctor to specifically tie off the area. Another treatment is the stapled hemorrhoidectomy, in which a special device is used to pull the hemorrhoid tissue back into the body and staple it in place.

External hemorrhoids

External hemorrhoids are veins that lie just under the skin on the outside of the anus. Usually, they do not cause any symptoms. Occasionally, a blood clot can form and can be very painful. These are not dangerous blood clots that can travel to other organs. The biggest concern they raise is pain. Many times this will get better on its own. Sometimes, the clot is removed under local anesthesia in the doctor's office.

Anal fissure

An anal fissure is a split or tear in the lining of the anus that occurs after trauma. This can happen as a result of a hard stool or even diarrhea.

An anal fissure causes bleeding and intense burning pain after bowel movements. The pain is caused by spasms of the sphincter muscle, which is exposed to air by this tear. The pain with bowel movements has been described as the feeling of passing razor blades.

Fissures are the anal problem that is misdiagnosed most commonly. They are frequently mistaken for hemorrhoids.

Fissures often heal on their own. If they don't improve, your doctor can recommend an ointment or medication that will relieve the pain. In certain cases, surgery may be recommended if the tear does not heal because of excessive sphincter spasm.

An anal fissure is a split or tear in the lining of the anus. A perianal abscess is a pocket of pus that results from a blocked, infected anal gland.

Perianal abscess

The anal region has tiny glands on the inside of the anus that open and probably help with the passage of stool. When one of these glands becomes blocked, an infection may develop and there may be an abscess (a pocket of pus). Treatment includes draining the abscess, usually under local anesthesia in the doctor's office.


In about 50% of cases after a perianal abscess has been drained, a tunnel develops from the gland on the inside of the anus to the skin around the anus. This is called a fistula-in-ano. Fistulas drain mucous fluid onto the skin and blood. They rarely heal on their own and usually need surgery.

Other perianal infections

Hair in the region between the anal area and the tailbone can burrow under the surface and cause an infection called pilonidal disease. It may present as abscess in this area just below the tailbone, or as small draining openings. Usually surgery is needed to treat this problem.

Sexually transmitted infections (STIs) that can affect the anus include herpes, AIDS, chlamydia, and gonorrhea. Anal warts are small growths on the anal skin that look like tiny pink cauliflowers and are caused by a virus (HPV).

Colon and rectal disorders

Diverticular disease

Colonic diverticula are little out-pouchings or sacs in the bowel lining that occur when the lining gets pushed through weak spots in the muscle of the bowel wall. They usually appear in the sigmoid colon, where the large bowel exerts the highest pressure.

Colonic diverticula are small out-pouchings or sacs that push through weak spots in the muscle layers of the colon wall.

Diverticular disease is very common in Western societies and may be due to low-fiber Western diets. Diverticula rarely cause symptoms unless one of the sacs gets blocked and infected. This is called diverticulitis and occurs in about 10% of people with diverticula. There is occasionally bleeding in this area.

About half the patients who have complications of their diverticula will need surgery.

Polyps and cancer

Cancer of the colon and rectum is a major health problem in America today. It occurs when the cells in the lining of the large bowel grow and divide in an uncontrolled manner. Many factors contribute to this loss of control, including the environment, our diet, and genetics (what we inherit from our parents).

The first abnormality in the bowel in colon cancer is a polyp, a small growth that may look like a mushroom protruding from the lining tissue of the large bowel. There are many types of polyps, and not all are the type that turn into cancer. However, removing these polyps before they develop severe changes and grow can prevent the progression to cancer.

Polyps are small abnormal growths that protrude from the tissue lining the colon or rectum.

When cancer develops, it must be removed by surgery. Chemotherapy may be recommended for cancer of the colon or rectum. Certain cancers of the rectum may require radiation treatment.

With prompt, expert treatment, most people can be cured of colorectal cancer. Although people may worry about having to wear a colostomy bag on the abdomen to collect stool, very few people need a permanent colostomy bag.

Because colorectal cancer comes from polyps, a colonoscopy procedure can prevent colorectal cancer by finding and removing polyps. People at greater risk for colorectal cancer include those who have had polyps or cancers in the past, or those who have a family history of colorectal cancer.


Colitis is a group of conditions that cause inflammation of the large bowel.

Colitis is an inflammation of the inner lining of the colon.

There are several types of colitis, including:

Colitis causes diarrhea, rectal bleeding, abdominal cramps, and urgency (increased need to go to the bathroom). Treatment depends on the diagnosis, which is made by colonoscopy and biopsy (removal of cells or tissue for examination under a microscope).


Many diseases of the colon and rectum can be prevented or treated by seeking prompt medical care. People who have symptoms of any of these conditions should consult their doctor.

Most importantly, colon cancer is a preventable disease. The most important risk factor is having a direct family member who had colon cancer. Ask your doctor when you need an evaluation (usually a colonoscopy) to look for polyps. For people with no family history and no symptoms, the current recommendation is that everyone should have their first colonoscopy at age 45.


Last reviewed by a Cleveland Clinic medical professional on 07/05/2019.


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