VCUG (Voiding Cystourethrogram): How Is It Done?

A VCUG involves filling the bladder, via a catheter, with a fluid that is visible on X-ray (contrast), and taking a series of images during filling and voiding. If reflux is present, the contrast rises up along the ureter (the urine channel between the kidney and bladder) and reaches the kidney's collecting system; how far the backflow reaches and how much the ureter and renal pelvis dilate give the International Reflux Study Committee's grade I–V.

The child lies on the X-ray table; one parent (if not pregnant) may stay beside the child wearing a protective apron. The genital area is cleaned; a numbing gel is applied, and a very thin (5–6 F in infants, 8 F in older children), soft catheter is placed in the bladder. Inserting the catheter is the most uncomfortable moment of the procedure; it takes a few seconds, and afterward the catheter is not felt.

The procedure is done when there is no active urinary tract infection; if a febrile UTI was recently treated, antibiotic treatment must be finished and the urine must have cleared. Most centers request a urinalysis before the procedure, and some request a culture. If sedation is not planned, fasting is not necessary; the child can eat and drink normally.

• The child must be fever-free and infection-free; the most recent urinalysis/culture must be clean
• If the child is on antibiotic prophylaxis, don't skip it; if not, follow the short course of coverage the center recommends
• If sedation is not planned, fasting is not required
• If the child is constipated, treat it before the procedure
• Bring previous ultrasound and lab results, current medications, and any allergies with you
• Explain the procedure to the child beforehand; bring a change of clothes and diapers

VCUG uses X-rays, but in today's pediatric centers, pulsed fluoroscopy, low-dose digital equipment, and a narrow imaging field have markedly reduced the dose. Reported effective doses are low and vary by center, equipment, and the child's size; families are usually told the dose is roughly comparable to natural background radiation received over a few months. No known harm has been shown at this level; even so, the test is done only in children where the result will change the decision, and unnecessary repeats are avoided.

Contrast-enhanced voiding urosonography (ceVUS) is also done via a catheter, but uses an ultrasound contrast agent (microbubbles) instead of X-ray; it involves no radiation. It is equivalent to VCUG for detecting and grading reflux, and has been found more sensitive in some studies. It may be preferred especially in girls, for sibling screening, and for post-treatment checks; the urethra can also be assessed in male infants, but VCUG is still considered the priority test when PUV is suspected. The number of centers offering ceVUS domestically is still limited.