Voiding Cystourethrogram (VCUG)

A Voiding Cystourethrogram (VCUG) is a fluoroscopy-based examination that goes one step further than a regular cystogram: in addition to filling the bladder with contrast, the radiologist takes images during urination so the urethra and the act of voiding can be evaluated.

VCUG is most often performed in children with recurrent urinary tract infections to look for vesicoureteral reflux — urine flowing backward from the bladder into the ureters and kidneys. It is also occasionally used in adults to evaluate voiding problems or post-operative urethral abnormalities.

Common Indications for a VCUG

A VCUG is usually requested:

• After a child has had two or more urinary tract infections.
• After a single febrile urinary tract infection in a young child.
• When a kidney ultrasound shows dilated ureters or scarring suggesting reflux.
• In children with abnormal antenatal kidney ultrasound findings (such as hydronephrosis).
• In adults with suspected urethral stricture or post-operative anatomy questions.

What exactly does a VCUG show?

The test specifically shows:

• The bladder filling with contrast.
• Whether contrast travels backward up the ureters toward the kidneys (vesicoureteral reflux) and how high it goes.
• The shape of the urethra during urination — important for detecting valves in boys and strictures in adults.
• Whether the bladder empties completely.
• Any abnormalities of bladder shape or capacity.

Vesicoureteral reflux is graded I to V:

• Grade I — reflux only into the lower ureter.
• Grade II — reflux up to the kidney without dilatation.
• Grade III — mild dilatation of the ureter and kidney collecting system.
• Grade IV — moderate dilatation, with some loss of the sharp angles in the kidney.
• Grade V — gross dilatation and tortuosity of the ureter; significant kidney distortion.

Low-grade reflux often resolves with time as the child grows; high-grade reflux is more likely to need surgical intervention.

What happens during the procedure?

• The child (or adult) changes into a gown.
• They lie on the X-ray table. For young children, a parent is usually allowed to stay in the room wearing a lead apron.
• The radiographer or nurse gently cleans around the urethral opening.
• A thin catheter is passed into the bladder. This is the most uncomfortable part of the test — it usually lasts only a few seconds.
• Sterile iodine-based contrast is slowly run into the bladder until it is full.
• The radiologist watches the bladder fill on the fluoroscopy screen. Images are taken as the bladder fills, then while the child urinates (in young children, often onto absorbent pads on the table).
• The catheter is usually removed before voiding to allow a more natural urination.

The whole procedure typically takes 20 to 40 minutes.

How is the test made easier for children?

Imaging centres that do VCUGs regularly take steps to reduce distress:

• A parent is allowed in the room throughout.
• A child life specialist or paediatric nurse may help with distraction, books, or screens.
• Numbing gel can be applied around the urethral opening before catheterisation.
• Mild sedation is occasionally used for very anxious children, particularly for repeat studies.

It is appropriate to ask the centre what their approach is before the appointment.

Do I need to prepare?

For a child:

• No fasting needed.
• A parent should bring an extra change of clothes for the child.
• Familiar comfort items (a favourite toy, blanket, or device) are encouraged.
• Talk to the child age-appropriately about what will happen — the test is much less distressing for children who know broadly what to expect.

For an adult:

• No fasting needed.
• Wear comfortable clothing — you will change into a gown.
• Tell the team about any iodine contrast allergies.
• Tell the team if there is any chance of pregnancy.

Will the test be painful?

Most of the discomfort is the catheter insertion, which lasts a few seconds. Once the catheter is in place, the rest of the test is generally well tolerated. Children may find the urge to urinate while lying on a table uncomfortable or embarrassing — this is normal and the radiographer is experienced in making it as easy as possible.

After the test, some mild burning with urination may persist for a day or two and usually resolves on its own.

How long do the results take?

A radiologist usually reviews images during the procedure and shares a preliminary impression at the end. The formal written report typically reaches your doctor within 24 to 72 hours.

Are there risks?

What about alternatives like nuclear-medicine cystograms?

For some children — particularly those being monitored after a known diagnosis of reflux — a radionuclide cystogram (RNC) is used instead. RNC uses a small amount of radioactive tracer instead of iodine contrast and produces a lower radiation dose, but it shows less anatomical detail. The first-ever cystogram is usually a fluoroscopic VCUG; follow-up studies may be RNC depending on the question.

What are the important limitations and safety checks?

Fluoroscopy shows movement or anatomy during a specific examination, but it does not guarantee a diagnosis or exclude every abnormality. Image quality and interpretation can be limited by positioning, movement, body size, retained contrast, overlying structures, incomplete filling, or the patient's ability to complete the study. Further endoscopy, ultrasound, CT, MRI, laboratory testing, or tissue sampling may still be needed.

Fluoroscopy uses ionising radiation. Dose varies with the body area, examination complexity, equipment, patient size, and imaging time; the team should use the lowest exposure that still answers the clinical question. Tell the team before the examination if you are or may be pregnant. Pregnancy does not create a universal ban: the referrer and imaging team should decide whether to defer, modify, or proceed when the expected benefit outweighs the risk.

Contrast and preparation are procedure-specific. Barium, water-soluble iodinated contrast, intravenous contrast, and contrast placed into a joint, bladder, uterus, duct, or fistula have different risks. Tell the team about prior reactions, swallowing or aspiration problems, suspected perforation, kidney or thyroid disease, diabetes, medicines, and recent contrast studies. Do not fast, stop medicines, interrupt breastfeeding, or take bowel preparation or antibiotics based only on a general webpage; follow the center's written instructions.

Questions to ask the fluoroscopy team

• What exact question should this examination answer, and is a radiation-free or non-invasive alternative suitable?
• Which contrast route and agent will be used, and what preparation, pregnancy, breastfeeding, allergy, kidney, diabetes, or medicine instructions apply to me?
• Will a catheter, internal examination, sedation, or pain relief be needed, and may I stop the procedure if I am uncomfortable?
• What symptoms require urgent help afterward, when will the signed report be ready, and who will explain the result?

Sources and further reading

• RadiologyInfo.org: Fluoroscopy
• American College of Radiology: Manual on Contrast Media
• RadiologyInfo.org: Radiation safety for children

Conclusion

A VCUG is the standard test for vesicoureteral reflux in children and remains valuable for evaluating the urethra in adults. The brief discomfort of catheter insertion is balanced by the precise diagnostic information the test provides — particularly the grade of reflux, which directly drives the treatment plan. With a calm explanation and a supportive imaging team, most children tolerate the procedure better than parents expect.