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Medical Tests & Exams

X-Ray Exam: Voiding Cystourethrogram (VCUG)

What It Is

A voiding cystourethrogram (VCUG) uses a small amount of radiation to make images of a person’s urinary system.

After the patient’s bladder is filled with a liquid called contrast material, an X-ray machine sends beams of radiation through the abdomen and pelvis, and images are recorded on special film or a computer. These images help doctors see problems in parts of the urinary system, including the bladder, urethra (the tube connecting the bladder with the outside of the body), and the ureters (the tubes connecting the kidneys to the bladder).

X-ray images are black and white. Dense body parts that block the passage of the X-ray beam through the body, such as bones, appear white on the X-ray image. Contrast material also appears white, and when it fills the organs of the urinary system, it makes them visible. Softer body tissues, such as the skin and muscles, allow the X-ray beams to pass through them and appear darker. Air in the stomach and intestines appears black.

An X-ray technician or radiologist takes the X-rays using a technique called fluoroscopy. While the contrast material fills your child’s bladder, and then while your child 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 films is recorded.

Why It’s Done

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

It also can show whether the urine is moving in the right direction. Normally, urine flows from the kidneys down to the bladder through the ureters. When urine goes back up toward the kidneys, it’s called vesicoureteral (VU) reflux. A VCUG can detect VU reflux. Sometimes VU reflux only occurs while urinating (voiding), which is why the VCUG includes taking X-ray images while the bladder is being emptied.

Since VU reflux can cause urinary tract infections (UTIs), this test is sometimes recommended after a child has had a UTI. Although not all kids who have had UTIs have reflux, it’s important to find those who do, since the treatment may vary depending on the severity of reflux.


A VCUG doesn’t require any special preparation. Your child may be asked to remove some clothing and jewelry and change into a hospital gown because buttons, zippers, clasps, or jewelry might interfere with the image.

If your daughter is pregnant, it’s important to tell the X-ray 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 necessary, precautions can be taken to protect the fetus.

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


The procedure may take about 30 minutes, although actual exposure to radiation is usually only a few minutes.

Your child will be asked to enter a special room that will most likely contain a table and a large X-ray machine hanging from the ceiling. Parents are usually able to accompany their child to provide reassurance. If you stay in the room while the X-ray is being done, you’ll be asked to wear a lead apron to protect certain parts of your body.

The technician will position your child lying down on the table. A plain pelvic X-ray may be taken first, and the technician will step behind a wall or to an adjoining room to operate the machine.

The technician will then wash between your child’s legs, and will insert a tiny rubber tube called a catheter into the bladder through the small opening of the urethra (where urine comes out). The catheter will be used to fill your child’s bladder with contrast material. As the contrast material fills the bladder, the urethra and bladder will be seen on a screen, and X-ray pictures will be taken.

Your child will start to feel the need to urinate. Babies will empty their bladder automatically; older kids will be asked to hold it in until the bladder is full. At that point, your child will be asked to urinate, and the movement of the contrast material in the urinary system will be watched on the monitor. X-ray pictures will be taken until the bladder is empty. When the study is completed, the catheter will be removed.

What to Expect

Your child will feel cool wet soap as the genital area is cleaned. The insertion of the catheter might feel uncomfortable and might make your child feel the urge to urinate. Once the catheter is in place, it’s usually painless.

Your child won’t feel anything as the X-rays are taken. The X-ray room may feel cool due to air conditioning used to maintain the equipment.

Babies often cry in the X-ray room, especially if they’re restrained, but this won’t interfere with the procedure.

After the X-ray is taken, you and your child will be asked to wait a few minutes while the image is processed. If it’s blurred or unclear, the X-ray may need to be redone.

Your child might complain of stinging while urinating the first couple of times after the procedure. Drinking extra fluids can help.

Getting the Results

The X-rays will be looked at by a radiologist (a doctor who’s specially trained in reading and interpreting X-ray 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 directly to the patient or family at the time of the test.


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 minimum amount of radiation required to perform the study properly.

Developing babies are more sensitive to radiation and are at more risk for harm, so if your daughter is pregnant, be sure to tell her doctor and the X-ray technician.

Helping Your Child

You can help your child prepare for a VCUG by explaining the test in simple terms before the procedure. If your child is old enough to understand, be honest about the brief discomfort that he or she may feel, but reassure your child that you’ll be right there for support. Some kids need a distraction (toys, books, bubbles, etc.) during the procedure, while some want to watch what’s going on. Others may cry and might need more reassurance.

Toddlers and preschoolers (and some older children) may benefit from a mild sedative to facilitate catheter placement. Please discuss the option of sedation with your physician if you feel that your child would benefit.

You can describe the room and the equipment that will be used; with older kids, be sure to explain the importance of keeping still while the X-rays are taken so they won’t have to be repeated. It may help to explain that once the catheter is in place, getting the X-ray is like posing for a picture or a video.

If You Have Questions

If you have questions about why the VCUG is needed, speak with your doctor. You can also talk to the X-ray technician before the procedure.

Reviewed by: Yamini Durani, MD
Date reviewed: May 2014