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Procedures: Ultrasound
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General Introduction
Ultrasonography or ultrasound scanning
involves the application of an ultrasound transducer on the area to be
examined. The transducter is used to transmit high-frequency sound waves,
which bounce off internal structures to produce an image that can be displayed
and recorded.
There are different versions of ultrasound scanning that are used in pregnancy
and to help diagnose certain gynaecological problems. These include a
(pelvic
ultrasound scanning or sonography), and a (endovaginal ultrasound or ultrasonography).
Pregnancy
Ultrasound
Description and Purpose
A pregnancy ultrasound, also known as pelvic ultrasound
scanning or sonography, consists of high-frequency sound waves, which
provide an image, a sonogram, similar to an X-ray. The sonogram shows
the baby's entire body, organs, and the surrounding tissues. A pregnancy
ultrasound is used for the following reasons:
- To and , evaluate their size and well-being, determine the
location of the ,
establish the amount of , and detect abnormalities in the foetus and mother's pelvis
(e.g. ).
- If the baby is at risk of inheriting a , to determine the sex of the baby (usually possible from
16th to 18th week).
- To reveal foetal malformations and severe disorders such as spina
bifida.
- May be performed to monitor foetal growth in late pregnancy.
- To assist in other procedures, such as ,
,
and , that require placement of a needle in the uterus.
Preparation and Procedure
If the test is performed early into the pregnancy
(i.e. during the first trimester), the woman will be asked to drink a
lot of fluids beforehand in order to have a full bladder. This is because
the full bladder descends, thus allowing a better view of the ,
as well as the fact that the fluid is a good medium for the transmission
of sound waves.
Later in pregnancy, a full bladder is not necessary, since the amniotic
fluid provides the medium, and the enlarged uterus not only pushes the
bladder down but extends so that it lies directly against the abdomen.
During the procedure, gel is applied to
the abdomen, and an ultrasound transducer (used to transmit high-frequency
sound waves, which bounce back to produce an image that can be recorded
on X-ray film) is moved across the abdomen. The image is relayed in real
time to a screen, which the doctor observes (for the reasons stated above).
The sonogram, can be printed on film or paper or recorded on videotape,
to be examined more carefully later, although the doctor may analyse the
scan immediately during the procedure. The whole procedure takes between
15 minutes and 1 hour, in general.
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| Advantages |
Disadvantages |
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It entails no exposure to X-ray
radiation.
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It's non-invasive.
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It produces quick results.
- It creates a moving image.
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Less reliable than amniocentesis
or CVs in diagnosing certain disorders, such as Down
syndrome.
- False-positive and false-negative
results are possible.
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For more complete and additional information
on this technique, contact the source for this page.
The information in this page is presented in summarised form and has been taken
from the following source(s):
1.
The Yale University School of Medicine Patient's Guide to
Medical Tests, Barry L. Zaret M.D., Senior Editor, published by Houghton Mifflin.
Online: http://www.collectivemed.com/jump/mtest.shtml
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Introduction
