Colonoscopy
A colonoscopy is a procedure for viewing the interior lining of
the large intestine (colon) using a small camera called a colonoscope (which is a flexible
fiber-optic tube).
How colonoscopy is performed
You lie on your left side with your knees drawn up toward the
abdomen. After administration of an intravenous sedative and analgesic, the instrument is
inserted through the anus and gently advanced under direct vision to the terminal small
bowel.
Air will be inserted through the scope to provide a better view. Suction may be used to
remove secretions.
Since better views are obtained during withdrawal than during insertion, a more careful
examination is done during withdrawal of the scope. Tissue samples may be taken with tiny biopsy forceps inserted through the scope. Polyps can be removed
with electrocautery snares, and photographs can be taken.
Specialized procedures, such as laser therapy, can also be performed.
How to prepare for a colonoscopy
Thorough cleansing of the bowel is mandatory. Instructions for
doing so will be given by the health care provider. This will include using enemas,
abstaining from all solid foods 2 or 3 days before the test, and taking laxatives.
To avoid dehydration, drink plenty of clear liquids (such as juices and broths). Unless
otherwise instructed, continue taking any regularly-prescribed medication. Discontinue
taking iron preparations a few weeks before the test, unless otherwise instructed by the
health care provider (iron residues produce a dark black stool, which inhibits the view).
Complete emptying of the colon before the examination requires enemas or other purgatives.
These must be repeated until no solid matter remains. An intravenous infusion and an
injection will be given to administer a pain reliever and a sedative during the procedure.
People with valvular heart disease may receive antibiotics before and after the test to
prevent infection. Outpatients must plan to have someone take them home after the test, as
they will be woozy and unable to drive.
Infants and children:
The physical and psychological preparation you can provide for this or any test or
procedure depends on your child's age, interests, previous experiences, and level of
trust. For specific information regarding how you can prepare your child, see the
following topics as they correspond to your child's age: From the Nation Institutes
of health.
How a colonoscopy will feel
The sedative and pain medication will provide relaxation and
produce a drowsy feeling. A rectal examination usually precedes the test to dilate the
rectum and make sure there are no major obstructions. You may have the urge to defecate
when the rectal exam is performed or as the colonoscope is inserted.
You may feel pressure as the scope moves inside. Brief cramping and gas pains may be
experienced as air is inserted or as the scope advances. The passing of gas is necessary
and should be expected.
Discomfort may be lessened by taking slow, deep breaths. This will also help relax the
abdominal muscles. Mild abdominal cramping and considerable passing of gas may occur after
the exam. Medications will produce sedation, which should wear off in a few hours.
Why the test is performed
- to obtain tissue specimen for biopsy
- to evaluate unexplained blood in the stool, abdominal pain, persistent diarrhea, or
abnormalities (such as polyps) found on contrast X-rays (barium enema)
- to determine the type and extent of inflammatory bowel disease (ulcerative colitis and
Crohn's disease)
- to follow people with previous polyps, colon
cancer, or a family history of colon cancer
Normal Values
Normal findings are simply healthy intestinal tissues.
What abnormal results mean
- lower gastrointestinal (GI) bleeding
- polyps (which can be removed through the colonoscope during the exam)
- tumor
- inflammatory bowel disease
- diverticulosis (particularly in older people)
Additional conditions under which the test may be performed:
- CMV gastroenteritis/colitis
- colon cancer screening
- colorectal polyps
- ischemic colitis
- pseudomembranous colitis
What the risks are
- bowel perforation, requiring an operation to repair the hole (less than 2 out of 1,000
tests)
- heavy or persistent bleeding from biopsy or polypectomy sites
(1 out of 1,000 tests)
- adverse reaction to sedative medication causing respiratory depression or low blood
pressure (4 out of 10,000 tests)
- infection requiring antibiotic therapy (very rare)
- nausea, vomiting, bloating, and rectal irritation caused by oral purgatives
Special considerations
You must sign an informed consent form. Several hours rest is
recommended after the test. To replace fluids lost because of laxatives and fasting, drink
plenty of liquids after the test. |