| Pediatric Voiding Cystourethrogram
What is a Voiding Cystourethrogram? Back to Top
A voiding
cystourethrogram (VCUG) is an x-ray examination of the bladder and
lower urinary tract. A catheter is inserted through the urethra, the
urinary bladder is filled with a water-soluble contrast material, and
the catheter is withdrawn. Several x-ray images of the bladder and
urethra are captured as the patient empties the bladder. These images
allow radiologists to diagnose any abnormalities in the flow of urine
through the body.
What are some common uses of the procedure? Back to Top
In
children, a voiding cystourethrogram is often recommended after a
urinary tract infection to check for a condition known as
vesicoureteral (VU) reflux.
Urine is produced in the kidneys and flows through the ureters into
the bladder. A valve mechanism prevents urine from backing up into the
kidneys as the bladder gets full. Urine leaves the bladder through the
urethra and is eliminated from the body during urination.
In some children an abnormality in the valve or the ureters allows
urine to flow backwards into the ureters, referred to as VU reflux. In
mild cases urine backs up into the lower ureter. In severe cases it can
back up into a swollen kidney.
Usually children with this condition are born with it. Other causes
can include blockage to the bladder, abnormal urination with very high
pressure within the bladder, incomplete emptying of the bladder, or
urinary tract infections. Reflux is commonly associated with urinary
tract infections, occurring in about 40 percent of newborns and
infants, and 25 percent of older children. Urinary tract infection may
be the only symptom of the problem.
How should my child be prepared for the procedure? Back to Top
Because
a voiding cystourethrogram (VCUG) is an x-ray procedure, metal objects
can affect the image, so avoid dressing your child in clothing with
snaps or zippers. Replace metal diaper pins with adhesive tape. No
other special preparation is required. Sedation is rarely needed and is
not desirable because it is important to be able to watch the child
urinate during the examination.
What does the x-ray equipment look like? Back to Top
The
equipment used for a voiding cystourethrogram consists of a large, flat
table. A moveable apparatus extends over a portion of the table and
sends real-time x-ray images to a television monitor. The radiologist
and technologist obtain multiple still images 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.
How does the procedure work? Back to Top
Very small,
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 x-rays that pass through the patient, an image
of the inside of the body is captured. The tissues of the urinary tract
are similar in density, so a contrast material is used to help produce
clearer images.
How is the procedure performed? Back to Top
The technologist
begins by positioning your child on the table. Infants and young
children may be wrapped tightly in a blanket or other restraint to help
them lie still during the imaging.
One or more images are usually captured before the contrast material
is introduced. Your child will be cleaned with special soap and a
small, sterile tube is placed through the urethra into the bladder. The
tube in the bladder is then connected to a bottle of a special contrast
material that is dripped by gravity until the bladder is filled. The
radiologist and/or the technologist watch a monitor while the bladder
is filling to see if any of the liquid goes backward into one or both
ureters.
After the bladder is filled, the catheter is removed and a series of
images are captured as your child empties his or her bladder. After
your child has voided completely, a final image is taken to see how
well the bladder empties.
What will my child experience during the procedure? Back to Top
A
voiding cystourethrogram is painless, though young children can be
frightened when they are tightly wrapped and unable to move. Before the
catheter is inserted, your child's genital area is scrubbed and
prepared with sterile materials, which may feel cold because of the
antiseptic used. Inserting the catheter and filling the bladder with
the liquid contrast material causes no pain but some children may
experience mild discomfort.
A parent is sometimes allowed to stay in the room to alleviate fear
but will be required to wear a lead apron to prevent radiation exposure.
Who interprets the results and how do we get them? Back to Top
A
radiologist, who is a physician experienced in radiology examinations,
will analyze the images and send a signed report with his or her
interpretation to your child's pediatrician or primary care physician.
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
- Voiding cystourethrogram (VCUG) images provide valuable,
detailed information to assist physicians in diagnosing and treating
urinary tract conditions to prevent kidney damage.
- Imaging of the urinary tract with VCUG is a minimally invasive procedure with rare complications.
A VCUG can often provide enough information to direct treatment with medication and avoid more invasive surgical procedures.
- The
imaging process is fast, painless and less expensive than alternatives
such as computed tomography (CT) and magnetic resonance imaging (MRI).
Risks
- X-rays are a type of electromagnetic radiation, are
invisible, and create no sensation when they pass through the body.
Modern x-ray techniques use only a fraction of the x-ray dose required
in the early days of radiology.
- Special care is
taken during x-ray examinations to ensure maximum safety for the
patient by restricting the x-ray exposure to only the part of the body
being examined.
- For a child that is 5-10 years old,
the effective radiation dose from this procedure is about 1.6 mSv,
which is about the same as the average person receives from natural
background radiation in 6 months. For an infant, the effective
radiation dose from this procedure is about 0.8 mSv, which is about the
same as the average person receives from background radiation in 3
months. See the Safety page for more information about radiation dose.
Radiation risks are further minimized by:
- 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 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 that are not being imaged receive minimal exposure.
-
What are the limitations of a Voiding Cystourethrogram? Back to Top
A
voiding cystourethrogram cannot evaluate obstruction of flow of urine
from the kidneys. Additional examinations are needed if obstruction is
suspected.
A voiding cystourethrogram should not be performed while an active, untreated urinary tract infection is present. Back to Top |
