What is a Voiding Cystourethrogram?

A voiding cystourethrogram (VCUG) is an x-ray examination of the bladder and lower urinary tract that uses a special form of x-ray called fluoroscopy and a contrast material.

An x-ray (radiograph) is a noninvasive medical test that helps physicians diagnose and treat medical conditions. Imaging with x-rays involves exposing a part of the body to a small dose of ionizing radiation to produce pictures of the inside of the body. X-rays are the oldest and most frequently used form of medical imaging.

Fluoroscopy makes it possible to see internal organs in motion. When the bladder is filled with and then emptied of a water-soluble contrast material, the radiologist is able to view and assess the anatomy and function of the bladder and lower urinary tract.

What are some common uses of the procedure?

A voiding cystourethrogram enables a radiologist, a physician specifically trained to supervise and interpret radiology examinations, to detect abnormalities in the flow of urine through the urinary tract.

This examination is often recommended after a urinary tract infection to check for a condition known as vesicoureteral (VU) reflux.

About VU Reflux

Urine is produced in the kidneys and flows through the ureter, the tube that carries urine from each kidney to 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, a condition called 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 include:

  • blockage to the bladder
  • abnormal urination with very high pressure within the bladder
  • incomplete emptying of the bladder
  • urinary tract infections

Urinary tract infection may be the only symptom of the problem.

How should we prepare?

You should inform your physician of any medications you are taking and if you have any allergies, especially to contrast materials. Also inform your doctor about recent illnesses or other medical conditions.

Clear liquids only for 24 hours prior to the exam. Nothing to drink after midnight.

  • List of appropriate clear liquids and some prohibited items are listed as well:
    • Coffee and tea – sugar is fine and small amount of creamer
    • Fruit and vegetable JUICES – strain to remove fibers/solids

DO NOT drink TOMATO juice.

    • Broths – must be semi-clear – chicken, beef or veggie

NO tomato soup and no solids in the soup.

    • Soft Drinks – Coke, Sprite, ginger ale, 7-up, etc. are allowed.
    • Gatorade, Crystal Light, Kool-aide, Propel, etc. are allowed.
    • Jello without any added fruit is allowed – DO NOT eat the red or purple version.
    • Popsicles are allowed – DO NOT eat the red or purple version.
    • Hard candies are allowed – DO NOT eat the red or purple version.


Bowel prep – Over the counter laxative of patient’s choice taken the early evening prior to the exam. Take per package instructions.

Because a voiding cystourethrogram (VCUG) is an x-ray procedure, metal objects can affect the image. You will be asked to wear a gown during the exam and to remove jewelry and eye glasses.

What does the equipment look like?

The equipment used for this examination consists of a radiographic table, an x-ray tube and a television-like monitor that is located in the examining room. When used for viewing images in real time (called fluoroscopy), the image intensifier (which converts x-rays into a video image) is suspended over a table on which the patient lies. When used for taking still pictures, the image is captured electronically.

A catheter, a flexible, hollow plastic tube, will be used to fill the bladder with a water-soluble contrast material.

How does the procedure work?

X-rays are a form of radiation like light or radio waves. X-rays pass through most objects, including the body. Once it is carefully aimed at the part of the body being examined, an x-ray machine produces a small burst of radiation that passes through the body, recording an image on a special digital image recording plate.

Fluoroscopy uses a continuous x-ray beam to create a sequence of images that are projected onto a fluorescent screen, or television-like monitor. When used with a contrast material, which clearly defines the area being examined by making it appear bright white, this special x-ray technique makes it possible for the physician to view internal organs in motion. Still images are also captured and stored either on film or electronically on a computer.

Until recently, x-ray images were maintained as hard film copy (much like a photographic negative). Today, most images are digital files that are stored electronically. These stored images are easily accessible and are sometimes compared to current x-ray images for diagnosis and disease management.

How is the procedure performed?

This examination is usually done on an outpatient basis.

The technologist begins by positioning you 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.
Several x-rays are taken of the bladder. Then, after cleaning the genital area, a catheter is inserted through the urethra, a tube that carries urine from the bladder out of the body, into the bladder, which is filled with a water-soluble contrast material.

The radiologist and/or the technologist will watch the fluoroscopic monitor while the bladder is filling to see if any of the liquid goes backward into one or both ureters. Several x-ray images of the bladder and urethra are then taken as you empty your bladder. A final x-ray is taken when you have voided completely.

You must hold very still and may be asked to keep from breathing for a few seconds while the x-ray picture is taken to reduce the possibility of a blurred image. The technologist will walk behind a wall or into the next room to activate the x-ray machine.

When the examination is complete, you will be asked to wait until the radiologist determines that all the necessary images have been obtained. A voiding cystourethrogram is usually completed within 30 minutes.

What will I experience during and after the procedure?

A voiding cystourethrogram is painless, though young children can be frightened. The antiseptic used to clean and prepare for the insertion of the catheter may feel cold. Some people may experience mild discomfort when the catheter is inserted and the bladder is filled with the liquid contrast material.

A parent is allowed to stay in the room to comfort the child but will be required to wear a lead apron to prevent radiation exposure.

Who interprets the results and how do we get them?

A radiologist, a physician specifically trained to supervise and interpret radiology examinations, will analyze the images and send a signed report to your primary care or referring physician, who will discuss the results with you.

What are the benefits vs. risks?

  • 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, avoiding 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).
    • No radiation remains in a patient’s body after an x-ray examination.
    • X-rays usually have no side effects in the diagnostic range.
  • Risks
    • There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk.
    • 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.

What are the limitations of a voiding cystourethrogram?

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.