Alternate Names : Sigmoidoscopy
A colonoscopy is a test where a flexible fiber optic
instrument is inserted into the colon, also called the large intestine.
This instrument is called a
colonoscope. It is a long, thin tube with a camera and light on the end.
With it, a doctor can view the inner surface of the colon.
The doctor can also sample or remove abnormal growths
through the colonoscope.
Who is a candidate for the test?
A colonoscopy may be recommended for a person with:
a change in bowel habits
which are small growths on the intestinal wall that may lead to cancer
a history of colorectal cancer
mucus, pus, or blood in the stool
prolonged or unexplained diarrhea
A colonoscopy may also be recommended for someone at high
risk for colorectal cancer.
This may include a person who has a strong family history of colorectal
cancer or polyps.
How is the test performed?
The person may be given medicine to make him or her drowsy or
more comfortable during the procedure. The person lies on one side with
knees flexed toward the abdomen. The doctor inserts the colonoscope
through the anus and up into the large intestine. The instrument is pushed
through the colon until it comes to the place where the colon meets the
At that point, air is passed through
the colonoscope to gently inflate the colon. This gives the doctor a clear
view of the inner lining of the colon. The doctor then
withdraws the instrument slowly, while examining all regions of the colon
along the way. Places of interest on the interior of the colon are sometimes
If the doctor sees
tissue that looks abnormal, a biopsy,
which is a small tissue sample, may be taken. Small colorectal polyps can also be
removed through the colonoscope.