Sigmoidoscopy can help diagnose:

• inflammatory bowel disease
• bowel obstruction
• colon cancer
• colon polyps
• diverticulosis
• causes of diarrhea
• causes of abdominal pain

Sigmoidoscopy can also be used to:

• determine the cause of blood, mucus, or pus in the stool
• confirm findings of another test or X-rays
• take a biopsy of a growth

What is a Sigmoidoscopy used for?

Sigmoidoscopy is used most often in screening for colorectal cancer or to determine the cause of rectal bleeding. It is also used in diagnosis of inflammatory bowel disease.

Cancer of the rectum and colon is the second most common cancer in the United States. About 155,000 cases are diagnosed annually. About 55,000-60,000 Americans die each year of colorectal cancer.

A number of studies have suggested, and it is now recommended by cancer authorities, that people over 50 be screened for colorectal cancer using endoscopy every three to five years. Individuals with inflammatory bowel disease, such as Crohn's disease or ulcerative colitis, who are at increased risk for colorectal cancer, may begin their screenings at a younger age, depending on when their disease was diagnosed. Many doctors screen such patients more often than every three to five years. Those with ulcerative colitis should be screened beginning 10 years after the onset of disease; those with Crohn's disease beginning 15 years after the onset of disease. Screening should also be done in patients who have a family history of colon or rectal cancer or small growths in the colon (polyps).

Some doctors prefer to do this screening with a colonoscope, which allows them to see the entire colon. However, most doctors prefer sigmoidoscopy, which is less time consuming, less uncomfortable, and less costly.

Studies have shown that one quarter to one-third of all precancerous or small cancerous growths can be seen with a rigid sigmoidoscope. About one-half are found with a 1 ft (30 cm) scope, and two-thirds to three-quarters can be seen using a 2 ft (60 cm) scope.

Description of a Sigmoidoscopy

Most sigmoidoscopy is done with a flexible fiber-optic tube. Because of this, the procedure is usually called flexible sigmoidoscopy.

The tube contains a light source and a camera lens. The doctor moves the sigmoidoscope up beyond the rectum (the first 1 ft/30 cm of the colon), examining the interior walls of the rectum. If a 2 ft/60 cm scope is used, the next portion of the colon can also be examined for any irregularities.

In a colorectal cancer screening, the doctor is looking for polyps. Studies have shown that over time, many of these polyps develop into cancerous lesions and tumors.

These cancerous or precancerous polyps can either be totally removed or biopsied during the sigmoidoscopy, using instruments threaded through the fiber-optic tube. People who have cancerous polyps removed can be referred for full colonoscopy, or more frequent sigmoidoscopy, as necessary.

In using sigmoidoscopy as a diagnostic tool, the doctor is looking for signs of ulcerative colitis, which include a loss of blood flow to the lining the bowel, a thickening of the lining, and sometimes a discharge of blood and pus mixed with stool. The doctor can also look for Crohn's disease with active involvement of the colon, which often appears as ulcerations that can run from tiny and shallow to large and deep, as well as erosions or "fissures" in the lining of the colon.

In many cases, these signs appear in the first few centimeters of the colon above the rectum, and it is not necessary (and may be unwise) to do a full colonoscopic exam. A full colonoscopy may cause pain or bleeding in an individual with active inflammatory bowel disease.

The procedure takes 20-30 minutes. Preparation begins one day before the procedure. There is some discomfort, similar to that experienced when a doctor performs a rectal exam using a finger to test for occult blood in the stool (the other major colorectal cancer screening test). There is rarely pain, except for individuals with active inflammatory bowel disease.

Private insurance plans almost always cover the $150 to $200 cost of sigmoidoscopy for screening in healthy individuals over 50, or for diagnostic purposes. Medicare covers the cost for diagnostic exams, and may cover the costs for screening exams. Medicaid varies by state, but does not cover the procedure in most states. Some community health clinics offer the procedure at reduced cost, but this can only be done if a local gastroenterologist (a doctor who specializes in treating stomach and intestinal disorders) is willing to donate his or her time.

Abnormal results of a Sigmoidoscopy

For a cancer screening sigmoidoscopy, an abnormal result is one or more noncancerous or precancerous polyps, or clearly cancerous polyps. People with polyps have an increased risk of developing colorectal cancer in the future.

Small polyps can be completely removed. Larger polyps require the doctor to usually remove a portion of the growth for laboratory biopsy. Depending on the laboratory results, the patient is then scheduled to have the polyp removed surgically, either as an "urgent" matter if it is cancerous or as an elective surgery within a few months if it is noncancerous.

In a diagnostic sigmoidoscopy, an abnormal result shows signs of active inflammatory bowel disease, either a thickening of the intestinal lining consistent with ulcerative colitis, or ulcerations or fissures consistent with Crohn's disease.