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
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
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
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
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.