Colon Cancer Screening

Flexible Sigmoidoscopy and Colonoscopy

Flexible sigmoidoscopy is a procedure performed to examine the inside of the rectum and sigmoid colon (the lower part of the colon leading to the rectum). This is done with a sigmoidoscope , a flexible tube attached to a lighted, fiberoptic instrument. Colonoscopy is also used to examine the rectum and sigmoid colon, but goes all the way to the small intestine. It is performed with a colonoscope , which is similar to the sigmoidoscope, but longer. Both procedures are used to diagnose, and in some cases treat, bowel conditions.

Another procedure, called capsule endoscopy , is used to examine the small intestine through a tiny camera that is swallowed. The capsule, which is the size of a large vitamin tablet, provides video images of the small intestine. It is not used to screen for colorectal cancer.

Colorectal cancer (cancer of the rectum or colon) is the second leading cause of cancer death in the United States; however, 35,000 of the 50,000 lives lost each year could be saved through early detection made possible by flexible sigmoidoscopy. The American Cancer Society (ACS) recommends colorectal cancer screening by sigmoidoscopy, along with fecal occult blood testing, every three to five years in adults age 50 and older. The ACS also advises routine screening for people under 50 who are at risk for colon cancer, and for those individuals who have had polyps or certain cancers. Colonoscopy is recommended once every 10 years for adults aged 50 and older. Other reasons for a sigmoidoscopy or colonoscopy are to:

Locate sites of rectal bleeding and identify the causes
Identify infections
Find the cause of chronic diarrhea, persistent constipation, or abdominal pain
Evaluate patients with inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease
Explore the cause of a change in bowel habits, unexplained weight loss, or fever
Remove polyps or foreign bodies
Treat other bowel diseases
Follow up on cancer treatment

Understanding the Risks and Benefits

Benefits

Sigmoidoscopy and colonoscopy are widely considered to be safe, simple, short procedures that cause minimal pain and discomfort. The benefits far outweigh the risks.

Sigmoidoscopy can detect and remove polyps located anywhere in the lower part of the colon or rectum; these polyps may be an indication of other polyps or cancer higher in the colon. Because most colorectal cancers begin as small, benign (noncancerous) polyps that become malignant (cancerous) in five to 10 years, removal of polyps at this early stage can prevent the development of cancer.

Colonoscopy allows for thorough inspection of the entire colon and is the most effective procedure available for colon evaluation. It can detect and remove polyps located anywhere in the large intestine and allows direct examination of any bleeding, infected or inflamed areas. Colonoscopy can also be used with other diagnostic and therapeutic measures, such as biopsy.

Capsule endoscopy is relatively safe and painless and can provide information on parts of the intestine not visible through sigmoidoscopy or colonoscopy.

Risks

These studies carry an extremely rare risk of perforating the bowel wall. This serious complication occurs in about one in 100,000 cases of sigmoidoscopy. Perforation of the bowel wall occurs more frequently in colonoscopies—about one in 1,000 cases. There is also a small risk of minor bleeding after either procedure.

Capsule endoscopy is mostly risk-free. The capsule could become lodged if there is intestinal stricture (narrowing), but the risk is considered rare.

Understanding the Procedures

Before the procedures

Be certain to tell your doctor about any recent illnesses, current medications, or allergies to medications you have had. Also discuss any underlying medical conditions you may have, such as diabetes, heart disease, bleeding problems or pregnancy. He or she will evaluate this information before performing a sigmoidoscopy. If you currently have diverticulitis (an inflammation of diverticula [pouches] in the colon), you should not undergo a sigmoidoscopy unless your health care provider believes the risks are justified.

If you are at risk for endocarditis (an infection of the tissue lining the heart), you may need to take an antibiotic before and after the procedure. Conditions that would put you at risk for this infection include a congenital (present at birth) heart defect, previous heart infection or having a prosthetic (man-made) valve.

Your health care provider may tell you to consume only clear liquids and/or take a laxative 24 hours prior to having a sigmoidoscopy. You also may be directed to have a cleansing enema before the procedure. Before a colonoscopy, your health care provider may instruct you to consume nothing but clear liquids for 48 to 72 hours prior to the procedure. Laxatives may be ordered from one to three days before the test. The night before, you may be instructed not to consume even clear liquids, and may also need to have an enema. An alternative bowel preparation involves taking a laxative or drinking a special cleansing solution.

The procedures

A sigmoidoscopy is performed by a primary care doctor, surgeon, internist or gastroenterologist (a doctor who specializes in digestive diseases). Flexible sigmoidoscopy usually takes 15 to 30 minutes and is done on an outpatient basis. Mild anesthesia or sedatives are rarely necessary. You will be asked to lie on your left side with your knees bent. Your health care provider will first perform a rectal exam, then insert the lubricated, flexible sigmoidoscope (which is about half an inch in diameter) into the anus and carefully advance it up the colon.

The sigmoidoscope is constructed to allow the physician to move it forward and backward or left and right. It has a light at one end to improve viewing and an opening at the other end for the removal of fluid from the bowel. A third opening allows the physician to introduce air into the colon; this inflation makes the colon's lining easier to see. The procedure may make you feel a slightly uncomfortable sensation of having to move your bowels or a mild cramping similar to gas cramps.

Your health care provider will look for abnormalities in the lining of the rectum and sigmoid colon and take biopsies of any suspicious areas. This involves removing a small sample of tissue. You will feel no pain when the biopsy specimen is taken. The tissue sample will be sent to a pathologist, who will study it under a microscope to determine whether the tissue is normal or abnormal. A final pathology report will be sent to your doctor, who will discuss the results with you.

Colonoscopies are much like sigmoidoscopies, although they are usually performed by surgeons or gastroenterologists, and may take a little more time (about 30 to 60 minutes). It is also done on an outpatient basis and mild anesthesia is usually given.

For capsule endoscopy, your doctor attached a recording device to your abdomen with adhesives, after which you swallow the capsule. You can leave the office and go about your daily routine immediately. The capsule passes through the digestive tract naturally, transmitting approximately 60,000 video images over a period of about 8 hours to the data recorder worn outside your body. You can usually take clear liquids about two hours after you swallow the capsule and a light meal may be eaten after four hours. Avoid vigorous physical activity or bending and do not go near devices that emit strong electrical signals, such as amateur radio sets, until the capsule is excreted. This usually takes about 24 hours; do not retrieve the excreted device. You can return the external equipment to your doctor's office after the procedure is complete. Your doctor will review the data and images recorded.

After the procedures

If you were given a sedative, you will need to wait for the effects to wear off and someone should drive you home. Otherwise, you will be free to leave immediately following the procedure and may resume all regular activities and return to work the same day. A bloated or gassy feeling a few hours afterward is normal and is a result of air injected into the colon during the procedure.

Final Note

Flexible sigmoidoscopy, colonoscopy and capsule endoscopy are useful tools for diagnosing, and in some cases treating, certain bowel conditions. Talk to your health care provider about whether any of them might be appropriate diagnostic tools for you.

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