Radiography - Lower GI Tract
(Barium Enema "BE")
What is Lower Gastrointestinal (GI) Tract Radiography?
This is an x-ray evaluation of the large intestine, also known as the colon.
This includes the right or ascending colon, the transverse colon, the left
or descending colon and the rectum. The appendix may be seen if it is present
and a portion of the small intestine may be visualized as well. Radiological
images are created by passing small, highly controlled amounts of radiation
through the body and capturing the resulting shadows and reflections on
film. Most people are familiar with x-ray images, which produce a still
picture of the body's internal organs. A similar imaging method, fluoroscopy,
uses x-rays to capture an image of an organ while it is functioning. Though
still x-ray images can be useful in examining the colon and rectum, dynamic
fluoroscopy is often the most effective way to view abnormal or blocked
movement of waste through the body's lower gastrointestinal (GI) tract.
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What are some common uses of the procedure?
A physician may order a lower
GI examination to look for ulcers, benign tumors (polyps, for example),
cancer, or signs of certain other intestinal illnesses. The procedure
is frequently performed on individuals suffering from chronic diarrhea,
blood in stools, constipation, irritable bowel syndrome, unexplained weight
loss, a change in bowel habits, or to detect a source of suspected blood
loss. Images of the bowel and colon are also used to diagnose inflammatory
bowel disease, a group of disorders that includes Crohn's disease and ulcerative
colitis.
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How should I prepare for the procedure?
You should tell your doctor about any recent illnesses or other medical
conditions, as well as any allergies you might have to medications. Women
should always inform their doctor or x-ray technologist if there is any
possibility that they are pregnant.
Your doctor will give you detailed instructions on how to prepare for your
lower GI imaging. During the day before the procedure, you will likely
be asked not to eat, and to drink only clear liquids like juice, tea, black
coffee, cola, or broth, and avoid dairy products. After midnight, you should
take nothing by mouth. You may also be instructed to take a laxative (in
either pill or liquid form) and to use an over-the-counter enema preparation
the evening, or even a few hours before the procedure. Just follow your
doctor's instructions. It is permissible to take usual prescribed oral
medication with limited amounts of water.
Once you arrive at the imaging center, you will be asked to change into
a gown before your examination. You may also be asked to remove jewelry,
eyeglasses, or any metal objects that could obscure the images.
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What does the x-ray equipment look like?
The equipment used for most lower GI examinations consists of a large, flat
table. A moveable apparatus extends over a portion of the table and sends
real-time images to a television monitor. Multiple static images are obtained
by the radiologist and technologist for later review. The table can move
and tilt and contains a drawer with a fluorescent plate that captures the
image and sends it to a nearby television monitor for viewing.
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How does the procedure work?
Very small, physician-controlled
amounts of x-ray radiation are passed through the body. Different
tissues—such
as bone, blood vessels, muscles, and other soft tissues—absorb x-ray
radiation at different rates. When a special film plate is exposed to the
absorbed x-rays, a detailed image of the inside of the abdomen is captured.
The tissues of the lower GI tract are similar in density, so a contrast
material is needed to provide exquisite detail of the inside of the colon.
Liquid barium, a dense, non-absorbable metallic solution, is introduced
into the colon through a rectal tube. The barium coats the inside of the
rectum, colon, and a part of the lower small intestine, and produces a
sharp, well-defined image.
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How is the procedure performed?
A lower GI radiological examination is often done on
an outpatient basis. The radiologist or technologist will discuss
details of the examination and can review rare contraindications (circumstances
that need special consideration). The patient is positioned on the
table, and a preliminary film is obtained to check for adequacy of the
bowel preparation. The radiologist or technologist will then make the contrast
material introduction through a small tube inserted into the rectum. A
mixture of barium and water is passed into the patient's colon through
the tube. To help the barium thoroughly coat the lining of the colon, air
may also be injected through the tube. In some circumstances, the radiologist
or referring physician may prefer a water and iodine solution rather than
barium to opacify the colon. Then a series of images is captured.
The patient may be repositioned frequently to enable the radiologist or
technologist to capture views of their colon from several angles. Some
equipment allows patients to remain in the same position throughout the
exam. During the study, the radiologist will monitor the delivery of barium
and take or request special views or close-ups.
Once the x-ray images are completed, most of the barium is drawn back into
a bag, and the patient is directed to the washroom to expel the remaining
barium and air. In some cases, the technologist may then take additional
images to help the doctor see how well the colon has cleared. The patient
is then released.
A lower GI study typically takes 30 to 60 minutes.
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What will I experience during the procedure?
As the barium fills your colon, you will feel the need to move your bowel.
You may feel abdominal pressure, or even minor cramping. These are common
sensations, and most people tolerate the mild discomfort easily. The tip
of the enema tube is specially designed to help you hold in the barium.
If you are having trouble, let the technologist know.
During the imaging process, you will be asked to turn from side to side,
and to hold several different positions. At times, pressure may be applied
to your abdomen. With air contrast studies of the bowel, the table may
be turned into an upright position.
You are able to return to a normal diet and activities immediately after
the exam. Your stools may appear white for a day or so, as your body clears
the metallic liquid from your system. You will be encouraged to drink additional
water for 24 hours after the examination. After a barium enema, some people
experience constipation. If you do not have a bowel movement for more than
two days after your exam, or are unable to pass gas rectally, call your
doctor promptly. You may need an enema or laxative to assist in eliminating
the barium, and your doctor will prescribe the right solution for you.
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Who interprets the results and how do I get them?
A radiologist, a physician experienced in GI studies and other radiology
examinations, will analyze the images and send a signed report with his
or her interpretation to your primary care or referring physician, who
will inform you on your test results. New technology also allows for distribution
of diagnostic reports and referral images over the Internet at many facilities.
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What are the benefits vs. risks?
Benefits
- With the use of the barium contrast material, lower GI imaging provides
valuable, detailed information to assist physicians in diagnosing
and treating conditions from normal to ulcers to cancer.
- X-ray imaging of the lower GI tract is a minimally invasive procedure
with rare complications.
- You may return to normal activity following the examination.
- The imaging process is fast and well-tolerated.
- Radiology examination can often provide enough information to avoid
more invasive procedures, such as colonoscopy.
Risks
- In rare cases, the barium suspension could leak through an undetected
perforation in the lower GI tract, producing inflammation
in surrounding tissues.
- Even more rarely, the barium can cause an obstruction in the gastrointestinal
tract, called barium impaction.
- The effective radiation dose from this procedure is about 4 mSv, which
is about the same as the average person receives from background
radiation in 16 months. See the Safety page for more information about
radiation dose.
- Women should always inform their doctor or x-ray technologist if there
is any possibility that they are pregnant.
Radiation risks are further minimized by:
- Special care that is taken during x-ray examinations to ensure maximum
safety for the patient by prudent, targeted application of
fluoroscopic radiation.
- The use of high-speed x-ray film that does not require much radiation
to produce an optimal image.
- Technique standards established by national and international guidelines
that have been designed and are continually reviewed by national
and international radiology protection councils.
- Modern, state-of-the-art x-ray systems (including mammography systems,
angiographic labs and CT scanners) that have very tightly controlled
x-ray beams with significant filtration and x-ray dose control methods.
Thus, scatter or stray radiation is minimized and those parts of a
patient's body not being imaged receive minimal exposure.
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What are the limitations of Lower GI Tract Radiography?
A barium enema is usually not indicated for someone who is in extreme abdominal
pain or had a recent colonic biopsy. If perforation is suspected, the enema
should be performed with the iodinated solution. X-ray imaging is not usually
indicated for pregnant women.
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