Voiding cystourethrography

Voiding cystourethrography (VCUG), also known as a micturating cystourethrography (MCU),  is a fluoroscopic study of the lower urinary tract in which contrast is introduced into the bladder via a catheter. The purpose of the examination is to assess the bladder, urethra, postoperative anatomy and micturition in order to determine the presence or absence of bladder and urethral abnormalities, including vesicoureteric reflux (VUR).

It is more commonly performed in the pediatric population than adults.


As per American College of Radiology (ACR) and Society for Pediatric Radiology (SPR) guidelines clinical indications for voiding cystourethrography include, but are not limited to:

Fever ≥39°C (102.2°F) and a pathogen other than E. coli after a first febrile urinary tract infection in a child is also considered a strong indication due to an increased risk of renal scarring in this population .


The estimated age-adjusted bladder capacity can be calculated using :

  • linear equations:
    • <1 year
      • weight [kg] x 7 = capacity (mL)
      • 2.5 × age [months] + 38  = capacity (mL)
    • <2 years: (age (years) + 2) x 30  = capacity (mL)
    • >2 years: ((age [years]/2)+6) x 30  = capacity (mL)
  • non-linear equations:
    • (4.5 x age [years]) x 30 = capacity [mL]
  • the bladder is filled with contrast medium using an infant feeding tube under aseptic precautions; a Foley catheter can be used for older children
  • intermittent screening of the patient on fluoroscopy, while distending the bladder with contrast, is necessary to check for a ureterocele or VUR
  • after the bladder is filled to its capacity (which will vary as per age of patient) the patient is now asked to void

The following projections should be acquired keeping within the ALARA principle:

  • AP with full bladder for demonstration of the presence or absence of VUR.
  • Both obliques to demonstrate bilateral vesicoureteric junctions.
  • Post-void film to check for a ureterocele.

    While the urethra is well outlined in both procedures, RUG/ASU is better to visualize anterior urethral abnormalities and VCUG is better for posterior urethral abnormalities. Additionally, VCUG is performed for detection of bladder abnormalities and vesicoureteric reflux (VUR). VCUG is the initial examination of choice after metoidioplasty or phalloplasty in transgender males (female to male) .

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