| Ultrasound - Abdomen
What is Abdominal Ultrasound Imaging? Back to Top
Ultrasound
imaging, also called ultrasound scanning or sonography, is a method of
obtaining images of internal organs by sending high-frequency sound
waves into the body. The reflected sound waves' echoes are recorded and
displayed as a real-time visual image. No ionizing radiation (x-ray) is
involved in ultrasound imaging. An abdominal ultrasound image is a
useful way of examining internal organs, including the liver,
gallbladder, spleen, pancreas, kidneys and bladder. Because ultrasound
images are captured in real time they can show movement of internal
tissues and organs and enable physicians to see blood flow. This can
help to diagnose a variety of conditions and to assess damage caused by
illness.
What are some common uses of the procedure? Back to Top
Ultrasound:Gallbladder
Ultrasound: Kidney
Ultrasound: Liver
Ultrasound imaging is used
extensively for evaluating the kidneys, liver, gallbladder, pancreas,
spleen and blood vessels of the abdomen. Because it provides real-time
images, it can also be used to:
- Guide procedures such as needle biopsies in which needles are used to sample cells from organs for laboratory testing.
- Help
a physician determine the source of many abdominal pains, such as an
inflamed appendix or stones in the gall bladder or kidney.
- Help identify the cause for enlargement of an abdominal organ.
Doppler ultrasound is a special type of ultrasound study that
examines major blood vessels. These images can help the physician to
see and evaluate:
- Blockages to blood flow, such as clots.
- Build-up of plaque inside the vessel.
- Congenital malformation.
- With
knowledge about the speed and volume of blood flow gained from an
ultrasound image, the physician can often determine whether a patient
is a good candidate for a procedure like angioplasty.
How should I prepare for the procedure? Back to Top
You
should wear comfortable, loose-fitting clothing for your ultrasound
exam. Other preparation depends on the type of examination you will
have. For some scans your doctor may instruct you not to eat or drink
for as many as 12 hours before your appointment.
What does the equipment look like? Back to Top
Ultrasound
scanners consist of a console containing a computer and electronics, a
video display screen and a transducer that is used to scan the body.
The transducer is a small hand-held device about the size of a bar of
soap, attached to the scanner by a cord. The radiologist or sonographer
spreads a lubricating gel on the patient's abdomen in the area being
examined and then presses the transducer firmly against the skin to
obtain images.
The ultrasound image is immediately visible on
a nearby screen that looks much like a computer or television monitor.
The radiologist or sonographer watches this screen during an
examination and captures representative images for storage. Often the
patient is able to see it as well.
An example of the ultrasound equipment that may be used is shown at the top of this page.
How does the procedure work? Back to Top
Ultrasound
imaging is based on the same principles involved in the sonar used by
bats, ships at sea and anglers with fish detectors. As a controlled
sound bounces against objects, its echoing waves can be used to
identify how far away the object is, how large it is, its shape and
internal consistency (fluid, solid or mixed), and how uniform it is.
The
ultrasound transducer functions as both a loudspeaker (to create the
sounds) and a microphone (to record them). When the transducer is
pressed against the skin, it directs a stream of inaudible,
high-frequency sound waves into the body. As the sound waves echo from
the body's fluids and tissues, the sensitive microphone in the
transducer records the strength and character of the reflected waves.
With Doppler ultrasound the microphone captures and records tiny
changes in the sound wave's pitch and direction. These signature waves
are instantly measured and displayed by a computer, which in turn
creates a real-time picture on the monitor. The "live" images of the
examination can be recorded on videotape or on disk. In addition, still
frames of the moving picture are usually "frozen" to capture a series
of images.
How is the procedure performed? Back to Top
The
patient is positioned on an examination table and a clear gel is
applied to the abdomen to help the transducer make secure contact with
the skin. The sound waves produced by the transducer cannot penetrate
air, so the gel helps to eliminate air pockets between the transducer
and the skin. The sonographer or radiologist then presses the
transducer firmly against the skin and sweeps it back and forth to
image the area of interest.
When the examination is complete
the patient may be asked to dress and wait while the ultrasound images
are reviewed, either on film or on a monitor. Often though, the
sonographer or radiologist is able to review the ultrasound images in
real time as they are acquired and the patient can be released
immediately.
What will I experience during the procedure? Back to Top
Ultrasound
imaging of the abdomen is painless, fast and easy. You will lie on your
back on an examining table. The radiologist or sonographer will spread
some warm gel on your skin and then press the transducer firmly against
your body, moving it until the desired images are captured. There may
be varying degrees of discomfort from pressure as the radiologist or
sonographer guides the transducer over your abdomen, especially if you
are required to have a full bladder. The examination usually takes less
than 30 minutes.
Who interprets the results and how do I get them? Back to Top
A
radiologist, who is a physician experienced in ultrasound and other
radiology examinations, will analyze the images and send a signed
report with his or her interpretation to the patient's referring
physician. The patient receives ultrasound results from the referring
physician who ordered the test results. In some cases the radiologist
may discuss preliminary results with you at the conclusion of your
examination. New technology also allows for distribution of diagnostic
reports and referral images over the Internet at many facilities.
What are the benefits vs. risks? Back to Top
Benefits
- Ultrasound scanning is noninvasive (no needles or injections in most cases) and is usually painless.
- Ultrasound is widely available and easy to use.
- Ultrasound
imaging uses no ionizing radiation and is the preferred image modality
for diagnosis and monitoring of pregnant women and their unborn
infants.
- Ultrasound provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies.
- Ultrasound images can visualize structure, movement and live function in the body's organs and blood vessels.
Risks
- For standard diagnostic ultrasound there are no known harmful effects on humans.
What are the limitations of Abdominal Ultrasound Imaging? Back to Top
Ultrasound
waves are reflected by air or gas; therefore ultrasound is not an ideal
imaging technique for the bowel. Barium exams and CT scanning are the
methods of choice for bowel-related problems in most cases.
Ultrasound
waves do not pass through air; therefore an evaluation of the stomach,
small intestine and large intestine may be limited. Intestinal gas may
also prevent visualization of deeper structures such as the pancreas
and aorta. Patients suffering from obesity are more difficult to
image—this is because tissue attenuates (weakens) the sound waves as
they pass deeper into the body.
Ultrasound has difficulty
penetrating bone and therefore can only see the outer surface of bony
structures and not what lies within and beyond. For visualization of
bone, other imaging modalities, such as MRI (magnetic resonance
imaging), may be selected. Back to Top |
