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Costas H. Kefalas, M.D., Northeastern Ohio Universities
College of Medicine, Rootstown, Ohio, and Digestive Health Center,
Akron, Ohio
Gastroenterologists often order radiographic tests to help diagnose
diseases of the gastrointestinal tract. Common complaints that
may lead to such testing include abdominal pain, nausea, vomiting,
heartburn, diarrhea, constipation, blood in the stool, bloating,
weight loss, and abnormal laboratory tests. This chapter describes
the more commonly performed radiographic tests.
Abdominal X-ray
An abdominal X-ray may be ordered to evaluate nausea, vomiting,
or abdominal pain, to exclude a blockage, perforation, or paralysis
of the intestinal tract. These X-rays may be performed in the standing
and flat positions. Organs absorb different amounts of the radiation
and this is seen on a film as varying degrees of black, white,
or gray. In some instances, another test, called a PET scan may
be ordered.
Barium Esophagram (Barium Swallow)
Barium studies, also called contrast studies, involve use of
a liquid agent that when swallowed provide an X-Ray image of the
inside of the intestine in relation to the wall of the organ and
surrounding structures Barium is a thick, white chalky substance.
A barium esophagram, or barium swallow, may be ordered for patients
with difficult or painful swallowing, coughing, choking, a sensation
of something stuck in the throat, or chest pain. The test is performed
when a patient drinks the barium and X-ray images or a video is
made. Sometimes you are asked to swallow a barium tablet if you
have trouble swallowing. This enables the doctor to detect a subtle
narrowing in the esophagus called a stricture.
Upper Gastrointestinal Series and Small Bowel
Follow Through X-ray
An upper gastrointestinal series is a barium study evaluating
the esophagus, stomach, and first part of the small intestine.
This test is ordered to search for causes of nausea, vomiting,
abdominal pain, or weight loss, to name a few. It is performed
much the same way as the barium esophagram, except additional time
is required to take pictures as the barium travels further in the
intestinal tract. A small bowel follow-through x-ray utilizes the
same principles and requires abdominal x-ray films to be taken
over many hours. This last test is often ordered to evaluate intestinal
bleeding of an unknown source, chronic diarrhea, or abdominal pain.
Barium Enema
A barium enema also requires the use of barium but in a different
manner. Patients must undergo a bowel-cleansing regimen (taken
orally) to eliminate residue from the colon. On the day of the
exam, a small tube is inserted in the rectum and barium contrast
is introduced throughout the colon. X-ray films are then made and
the colon anatomy is visualized. Abnormal findings may include
colon cancer, polyps, intestinal inflammation, and structural abnormalities
such as areas of narrowing (strictures) or diverticulosis, which
may explain the patient’s symptoms. The federal statute that
was enacted in 1997 to provide a colorectal cancer screening benefit
for Medicare beneficiaries envisions only limited use of barium
enema for colorectal cancer screening, essentially only for patients
who cannot or will not receive either a flexible sigmoidoscopy
or colonoscopy. In such a patient, Medicare rules permit a barium
enema if the patient’s physician attests that for this patient,
results of barium enema will be equivalent to or better than a
colonoscopy or flexible sigmoidoscopy.
Abdominal Ultrasound, Doppler Ultrasound,
and Doppler Mesenteric Ultrasound
An ultrasound is a non-invasive imaging test, which uses sound
waves to create images of organs. Normal and abnormal tissues and
organs contain different acoustic properties. When an abnormality
is present, such as a gallbladder stone or changes in the appearance
and size of the liver, as seen in cirrhosis, a characteristic appearance
is noted on the ultrasound. The test is performed with the placing
of an ultrasound probe onto the skin over the organ(s) of interest.
An abdominal ultrasound may evaluate the gallbladder, liver, bile
ducts, pancreas, kidneys, and the abdominal cavity. The addition
of a continuous sound wave, called “Doppler,” is done
to evaluate blood flow in vessels, both arteries, and veins. A
Doppler ultrasound of the liver determines if the veins to and
from the liver are open and not narrowed or obstructed. A Doppler
mesenteric ultrasound evaluates the three main arteries that carry
blood to the intestinal tract for any narrowing or stenosis.
Computed Tomography (CT) Scan and Computed
Tomography (CT) Angiography or Venography
A computed tomography scan, or CT scan, results in multiple high-resolution
cross-sectional images, (high quality pictures of the body as if
it were being sliced across the middle) every 5-10 millimeters,
which are created by movement between the X-ray beam and the film.
A computer then reconstructs the images. This exam is usually done
with oral contrast (usually barium), which the patient consumes
hours before the exam, and intravenous contrast (such as iodine),
which is intravenously injected into the patient at the time of
the exam. Gastroenterologists may order this test to evaluate abdominal
pain, to exclude an abscess (an area of infection), and to evaluate
organs such as the liver, pancreas, small intestine and colon.
A CT angiography or CT venography are specific CT scans that evaluate
either abdominal arteries or veins, respectively. These tests are
ordered when a condition with low blood flow to the intestinal
tract is strongly suspected.
Virtual Colonoscopy
Virtual colonoscopy, or more appropriately, virtual colonography,
employs the principles of computed tomography with image reconstruction
to produce a 3-D or “virtual” exam of the colon. This
test has received much attention over the last few years because
it has been suggested as an additional option for colon cancer
screening. This test requires a bowel preparation, is performed
without sedation, carries some reported risks of radiation exposure
and involves introducing air into the bowel through the rectum
which often produces patient discomfort. If an abnormality is noted
via a virtual colonoscopy, such as a polyp or growth within the
colon, a complete colonoscopy must then be done. At present, the
exam does not reliably detect small lesions in the colon. Some
advocates of this procedure maintain that the small polyps that
are not usually detectable via this technique, may be left in the
bowel without treatment, even if they are cancerous or precancerous.
This view is at odds with the more conservative posture of gastroenterologists
that all polyps pose a potential health risk, and need to be detected
and removed as early as possible.
Magnetic Resonance Imaging (MRI), Magnetic Resonance Cholangiopancreatography
(MRCP), and Magnetic Resonance Angiography
(MRA)
Magnetic resonance imaging, or MRI, is a noninvasive technique
that involves radiofrequency radiation in a high magnetic field
to produce high resolution images of the body in various directions.
A non-iodine contrast agent, usually gadolinium, is injected at
the time of the exam. This test is performed to evaluate intra-abdominal
organs, such as the liver or pancreas, for masses or cysts. When
the bile and pancreas ducts are examined with MRI, this test is
called MRCP. The arteries that carry blood to the intestinal tract
may be examined with a specific MRI known as MRA, or MR angiography.
Often times the MRI exam is done after an abnormality is found
on an ultrasound or CT scan or if additional information is needed
to explain a patient’s symptom.
Gastric Emptying Study
A gastric emptying study is a nuclear imaging study done to evaluate
the ability of the stomach to empty. Delayed gastric emptying,
or gastroparesis, may result from a number of conditions, most
commonly from diabetes mellitus. This may result in nausea, vomiting,
bloating, sensation of early fullness during eating, or abdominal
pain. The test is performed by administration of a meal that contains
small amounts of a substance usually technetium sulfur. Images
are taken of the stomach over time. Normally, within a set time,
a certain amount of gastric contents exits the stomach and empties
into the small intestine. This test demonstrates the amount of
contents remaining in the stomach, and if the amount is below the
established cut-off values, delayed stomach emptying is diagnosed.
Cholescintigraphy (HIDA Scan)
Another nuclear scan, cholescintigraphy, commonly known as a
HIDA scan, evaluates the function of the gall bladder. This test
may be ordered to diagnose or exclude acute or chronic inflammation
of the gallbladder, obstruction of the bile ducts, and the presence
of a bile leak. Nuclear contrast is injected intravenously and
images are taken. Much like a gastric emptying study, if the amount
of bile emptied from the gall bladder is below the normal range,
there may be a problem with gallbladder function.
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