Sigmoidoscopy

Sigmoidoscopy is a procedure in which a doctor looks in your rectum, sigmoid colon, and descending colon. A length of flexible tube connected to a fiberoptic camera is used. A light is transmitted through the scope to the tip by a bundle of light fibers. The doctor uses this light to look at your rectum, sigmoid colon, and part of your descending colon through an eyepiece or video screen. A colonoscopy is similar except that the doctor examines the entire length of your colon. This website will help you understand what is involved.

Individuals should discuss with their doctors the risks and benefits of all screening procedures. Some controversy exists over how often people without risk factors for cancer should be screened and which detection method should be used for them.

Guidelines for Adults Age 50 and Over with Average Risk. The following are the five screening options recommended by the National Cancer Institute for people age 50 and over who have no symptoms and no family history of colon cancer:

Fecal occult blood test (FOBT) or fecal immunochemical test (FIT) every year
Flexible sigmoidoscopy every 5 years
FOBT or FIT every year plus sigmoidoscopy every 5 years
Double-contrast barium enema every 5 years
Colonoscopy every 10 years

Choosing between Colonoscopy and Sigmoidoscopy. The choice between colonoscopy and sigmoidoscopy for routine screening for older adults with average risk is an area of intense debate. The issues are as follows:

Sigmoidoscopy is less costly, less invasive, quicker, and safer than colonoscopy. Although it allows inspection of only the left side of the colon, any abnormal findings from sigmoidoscopy trigger a full colonoscopy. Therefore, experts estimate that sigmoidoscopy can detect 80% of all significant problems.
Colonoscopy is more sensitive than any other current screening method for detecting colon cancer. It can find 75 - 90% of colorectal cancers. If the goal were to reduce the number of cancer cases, regardless of cost, colonoscopy would be the preferred approach. Colonoscopy, however, is more expensive than sigmoidoscopy and has a slightly higher risk for complications (bowel tears or bleeding when a polyp is removed).

Screening, particularly with colonoscopy, in increased- and high-risk populations can save lives. The most important risk factors are a family history of colorectal cancer and personal history of colorectal cancer, polyps, or chronic inflammatory bowel disease. People with these risk factors should be screened before age 50 and may need more frequent screenings.

Guidelines for Increased-Risk Groups. Anyone with first-degree relatives diagnosed with colon cancer younger than 60, or with two relatives who have been diagnosed with colon cancer at any age, should consider beginning the standard screening regimen with a colonoscopy every 5 years, beginning at age 40 or 10 years before the youngest case in the family (whichever is earlier).

Men of African descent are also considered to be at increased risk for colon cancer and should discuss similar screening guidelines with their doctors.

Guidelines for High-Risk Groups. The following guidelines may be useful for specific high-risk groups.

People who have the mutated hereditary nonpolyposis colorectal cancer gene (MSH2 or MLH-). Frequent colonoscopy (for instance, every 1 - 2 years) beginning in their early 20s. (Regular screening for other cancers, such as uterine cancer, is also reasonable.)
People who have the mutated familial adenomatous polyposis (FAP) gene. Frequent screening with endoscopy (flexible sigmoidoscopy or colonoscopy) beginning in early puberty. Genetic testing is now recommended for family members of people with known FAP.
People with predisposing intestinal problems, such as widespread and active ulcerative colitis or Crohn's disease. Annual screening with colonoscopy with biopsies of suspicious areas.

Guidelines for Follow-Up After Detection of Precancerous Polyps. Patients who have had a previous examination in which polyps were detected (and removed) should have a repeat colonoscopy 1 - 3 years later, depending on the size, number, and type of polyps removed.

This information is not meant to be medical advice. It is presented for informational purposes only. You need to consult with your physician about your own circumstances.