Colon Cancer Screening (cont.)
Flexible sigmoidoscopy
Flexible sigmoidoscopy utilizes a flexible sigmoidoscope, a flexible, fiberoptic viewing tube
with a light at the tip. It is inserted through the anus and is used by
the doctor to examine the rectum and the part of the colon adjacent to the rectum. It
is a shorter version of a colonoscope. Approximately 50% of colorectal cancers
and polyps are found to be within the reach of a flexible sigmoidoscope. It
is recommended that individuals of average risk for colon cancer undergo a
flexible sigmoidoscopy examination at age 50 and every 3-5 years thereafter. If
polyps are found during a flexible sigmoidoscopic examination, a colonoscopy to
examine the entire colon is recommended to remove the polyps as well as to find
and remove additional polyps in other parts of the colon. The removed polyps
are examined by a pathologist under a microscope to determine if the polyps
are benign, malignant or pre-cancerous. Individuals with precancerous
polyps (adenomas and villous adenomas) have a higher than average risk of
developing colon cancer, and it is recommended that they return periodically
for surveillance colonoscopies (see below). For more information about
this procedure, please see the Flexible
Sigmoidoscopy article.
Screening colonoscopy
Many doctors in the US are recommending screening colonoscopies rather than flexible
sigmoidoscopies for healthy subjects with an average risk for developing colon
cancer. Colonoscopies are recommended beginning at the age of 50 and thereafter every 7-10
years if no colon polyps or cancers are found. The rationale for this
recommendation is:
- Colonoscopy examines the entire colon while
flexible sigmoidoscopy only examines the rectum and the colon adjacent to the
rectum.
- Approximately 50% of colon polyps (and colon cancers)
are found in the upper colon (cecum, ascending colon, and transverse colon)
and, therefore, are beyond the reach of sigmoidoscopes and would be missed by
flexible sigmoidoscopy.
- The National Polyp Study, a large, scientific study, has shown that
colonoscopy with removal of all colon polyps reduces deaths from colon cancer.
For more information about this procedure, please see the Colonoscopy
article.
Next: Virtual colonoscopy »
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