Flexible sigmoidoscopy is a routine outpatient procedure in which the inside of the lower large intestine (called the sigmoid colon) is examined. Sigmoidoscopy is the procedure by which a doctor inserts either a rigid or flexible fiber-optic tube into the rectum to examine the lower portion of the large intestine (or bowel). The sigmoidoscope can be a short, rigid scope or a flexible scope of approximately 1-2 ft (30-60 cm). The latter is usually called a colonoscope.
Flexible sigmoidoscopies are commonly used to evaluate bowel disorders, rectal bleeding or polyps (usually benign growths). Sigmoidoscopies are also performed to screen people over age 50 for colon and rectal cancer. 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.
What's the preparation for sigmoidoscopy?
Before sigmoidoscopy is performed, the physician should provide educational materials and discuss the details of the examination with the patient. The physician must also review the risks of the procedure and obtain informed consent. A complete medical history should be obtained to ensure the appropriateness and safety of the examination. Although medications do not have to be withheld for sigmoidoscopy, the physician should be aware of any drugs the patient is taking.
The purpose of preparation for sigmoidoscopy is to clean the lower bowel of stool so the doctor can see the lining. Preparation begins 24 hours before the procedure, when the individual must begin a clear liquid diet. Preparation kits are available in drug stores. In normal preparation, about 20 hours before the exam, the individual is asked to take three tablespoons (about 1.5 oz) of Fleet Phospho-Soda laxative, mixed into 4 oz of water, followed by 24 oz of any other clear liquid. Four hours later, another 1.5 oz of the laxative are taken in 4 oz of water, followed by 8 oz more of clear liquid. The individual must stop drinking four hours before the exam.
For those who cannot tolerate the phospho-soda laxative and all the liquid (those with renal insufficiency or congestive heart failure) an alternative preparation uses one bottle of Citrate of Magnesia, taken about 20 hours prior to the exam.
Again, the individual must stop drinking four hours before the exam. Just prior to the exam, the individual uses two enemas to finish cleansing the lower bowel. Individuals need to be careful about medication before having sigmoidoscopy. They should not take aspirin, products containing aspirin, or ibuprofin products (Nuprin, Advil, or Motrin) for one week prior to the exam. They should not take any iron or vitamins with iron for one week prior to the exam. They should take any routine prescription medication, but may need to stop medication for diabetes.
What happens during the procedure?
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.
What're the complications of flexible sigmoidoscopy?
Flexible sigmoidoscopy and colonoscopy are very safe tests. Complications from flexible sigmoidoscopy are very rare. There is a slight risk of bleeding from the procedure. This risk is heightened in individuals whose blood does not clot well, either due to disease or medication, and in those with active inflammatory bowel disease. There are two main risks with colonoscopy. If a polyp is removed there can be bleeding; this usually settles but occasionally an operation may be required. During the examination the bowel is stretched by the instrument and it is possible for a puncture in the bowel wall to occur.