A voiding cystourethrogram (VCU) 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through the urethra, the urinary bladder is filled with a water-soluble contrast material, then the catheter is withdrawn.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?
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. Upon urination, urine leaves the bladder through the urethra and is eliminated from the body.
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?
Because a voiding cystourethrogram (VCU) 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 equipment look like?
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?
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?
The technologist begins by positioning your child on the table.
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 films 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?
Before the catheter is inserted, your child's genital area is cleansed and prepared with sterile materials, which may feel cold because of the antiseptic used. Inserting the catheter into the urethra causes a “stinging” sensation. Filling the bladder with the liquid contrast material causes no pain, but some children may experience mild discomfort as the bladder becomes distended.
A parent is 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?
Our radiologist, who is a physician experienced in radiology examinations, will analyze the images and fax a report with his or her interpretation to your child's pediatrician or primary care physician.
What are the benefits vs. risks?
- Voiding cystourethrogram (VCU) 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 VCU is a minimally invasive procedure with rare complications.
- A VCU can often provide enough information to direct treatment with medication and avoid more invasive surgical procedures.
- The imaging process is fast, relatively painless and less expensive than alternatives such as computed tomography (CT) and magnetic resonance imaging (MRI).
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 shielding the abdomen and pelvis with a lead apron, with the exception of those examinations in which the abdomen and pelvis are being imaged.
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.
Radiation risks are further minimized by:
The use of digital imaging 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.
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What are the limitations of a Voiding Cystourethrogram?
A voiding cystourethrogram should not be performed while an active urinary tract infection is present.