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Voiding Cystourethrogram (VCUG)

What Is a Voiding Cystourethrogram?

A voiding cystourethrogram (VCUG) is an exam that takes images of the urinary system.

The patient's bladder is filled with a liquid called contrast material. Then, images of the bladder and kidneys are taken as the bladder fills and also while the patient urinates (pees). These images help doctors see problems in:

  • the bladder, the muscular sac in the lower belly that holds pee
  • the urethra (yoo-REE-thruh), the tube connecting the bladder with the outside of the body
  • the ureters (YUR-uh-ters), the tubes connecting the kidneys to the bladder

How Is a Voiding Cystourethrogram Done?

The images for a voiding cystourethrogram (siss-toe-yuh-REE-thruh-gram) can be taken two ways: with an X-ray or an ultrasound.


An X-ray machine sends beams of radiation through the belly and images are recorded on a computer. X-ray images are black and white. Some body parts, such as bones, appear white on the X-ray. Some body parts, such as the kidneys and bladder, are hard to see on an X-ray. But the contrast material used for the test makes it much easier to see the urinary tract on the X-ray.

A radiologist takes the X-rays using a technique called fluoroscopy . While the contrast material fills the bladder, and then while the patient empties the bladder, the technician or radiologist watches an onscreen X-ray video of the liquid moving through the urinary system and a series of X-ray images are recorded.


Another way of doing a VCUG is with ultrasound. The sonographer places warm gel on the belly and an ultrasound probe on the patient's skin to get images. The bladder and kidneys are watched with the ultrasound and images are taken as the bladder is filled with contrast. Ultrasound is different from X-rays because it does not use radiation.

If your child needs a VCUG, your doctor will help decide which method is right for your child.

Why Are Voiding Cystourethrograms Done?

A VCUG can check for problems in the structure or function of the urinary system. It can check the bladder's size and shape and look for problems, such as a blockage along the path of the urine.

It also can show whether pee is moving in the wrong direction. Normally, pee flows from the kidneys down to the bladder through the ureters. When it goes the wrong direction (back up toward the kidneys), it's called vesicoureteral reflux (VUR). A VCUG can detect VUR. Sometimes this problem only happens when a person is urinating (voiding). That's one reason why the VCUG must include taking images while the bladder is being emptied.

Because VUR can cause urinary tract infections (UTIs), this test is sometimes recommended after a child has had a UTI. Not all kids who have had UTIs have reflux, but it's important to find those who do, because treatment may vary depending on the severity of reflux.

How Do We Prepare for a Voiding Cystourethrogram?

Some children over 1 year old may get sedation for the test. If your child has sedation, they must not eat or drink before the test. Talk to your doctor about whether sedation is needed.

Otherwise, a VCUG doesn't need any other special preparation. Your child may be asked to remove clothing and jewelry and change into a hospital gown because buttons, zippers, clasps, or jewelry might interfere with the images.

If your daughter is pregnant, it's important to tell the technician or her doctor. X-rays are usually avoided during pregnancy because there's a small chance the radiation may harm the developing baby. But if the X-ray is needed, precautions can protect the fetus.

It's also important to tell the technician if your child has any allergies, especially to contrast material.

What Happens During a Voiding Cystourethrogram?

A VCUG takes about 30–60 minutes.

The test is done in a special room with either an X-ray or ultrasound machine. Parents usually can stay with their child during the VCUG. A doctor also will be there, as well as either an ultrasound or X-ray technician.

The technician or doctor will wash between your child's legs, then insert a tiny rubber tube called a catheter into the bladder through the small opening of the urethra (where pee comes out). This might feel uncomfortable. When the catheter is in place, the rest of the test usually is painless.

The catheter is used to fill the bladder with the contrast material. As the bladder fills, it's viewed on a screen and pictures are taken. Your child will start to feel the need to pee as the bladder gets full. Babies will empty their bladder automatically. Older kids are asked to hold it in until the bladder is full. Then, they're asked to pee. The movement of the contrast material in the urinary system is seen on the screen and pictures are taken. When the bladder is empty, the catheter is removed.

Your child won't feel anything as the images are taken. Babies do often cry in the exam room if they are being held still for the pictures, but this won't interfere with the procedure.

Your child might complain of stinging while peeing the first few times after the test. Drinking extra fluids can help.

When Are the Results Ready?

A radiologist (a doctor trained in reading and interpreting X-ray and ultrasound images) will review the images. The radiologist will send a report to your doctor, who will discuss the results with you and explain what they mean.

In an emergency, the results of a VCUG can be available quickly. Otherwise, results are usually ready in 1–2 days. In most cases, results can't be given to the patient or family at the time of the test because the images need to be reviewed in detail.

What Are the Risks of Voiding Cystourethrogram?

In general, X-rays are very safe. Although there is some risk to the body with any exposure to radiation, the amount used in a VCUG is small and not considered dangerous. It's important to know that radiologists use the lowest amount of radiation needed to do the test.

If the test is done with an ultrasound, there is no radiation. Ultrasound is very safe and the FDA has approved the contrast material for use in VCUG studies.

How Can Parents Help?

You can help your child prepare for a VCUG by explaining the test in simple terms. If your child is old enough to understand, be honest about the brief discomfort they may feel, but reassure your child that you'll be there for support. A mild sedative can make the catheter placement easier for toddlers and preschoolers (and some older children). Ask your doctor about sedation if you think it might help your child.

You can describe the room and the equipment that will be used. With older kids, explain the importance of keeping still while the images are taken so they won't have to be repeated. It may help to explain that after the catheter is in place, getting the images is like posing for a picture or a video.

Some kids need a distraction (toys, books, bubbles, etc.) during the test, while some want to watch what's going on. Others may cry and might need more reassurance.

If you have questions about why the VCUG is needed or how the test is done, speak with your doctor. You can also talk to the technician before the procedure.

Reviewed by: Kathleen Schenker, MD
Date Reviewed: Jan 1, 2020

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