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.

Indications

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:

• urinary tract infection

• dysuria

• dysfunctional voiding

• hydronephrosis and/or hydroureter

• bladder outlet obstruction

• hematuria

• trauma

• urinary incontinence

• neurogenic dysfunction of the bladder, e.g. spinal dysraphism

• congenital anomalies of the genitourinary tract

• postoperative evaluation of the urinary tract

Previously history of urinary tract infection with fever ≥39°C (102.2°F) and infected by a pathogen other than E. coli  is also considered a strong indication for voiding cystourethrogaphy to look for the presence of vescioureteric reflux and renal scarring so treatment be initiated early ².

Procedure

The estimated age-adjusted bladder capacity can be calculated using ^4,5:

• 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) ⁶

  • >2 years: ((age [years]/2)+6) x 30  = capacity (mL)

• non-linear equations:

  • (4.5 x age [years]^0.40) x 30 = capacity [mL]

Technique

• the patient emptied the bladder before the examination ⁷

• a urinary catheter is inserted into the bladder. Infant feeding tube can be inserted under aseptic precautions for infants or young children; a Foley catheter can be used for older children ⁷

• contrast medium is slowly dripped or infused through the catheter into the bladder. The contrast is monitored initially confirm the position of the catheter ⁷

• intermittent screening of the patient on fluoroscopy, while distending the bladder with contrast, is necessary to check for a ureterocele or VUR ⁷

• after the bladder is filled to its capacity (which will vary as per age of patient), the catheter is removed and the patient is now asked to void. Younger children can void on absorber pad while older children can urinate on a urine receiver. Suprapubic pressure may be applied to increase the rate of voiding. The catheter should only be removed when it is confident that the patient is able to urinate, the patient unable to tolerate further infusion, or there is no more contrast medium for infusion ⁷

• spot images are taken to for any VUJ. The lower ureter is best seen in anterior oblique position. Oblique or lateral positions are also useful to visualize the whole of urethra ⁷

• abdominal view is taken to detect any reflux into the kidneys or record the postmicturition volume of the bladder ⁷

• lateral view is useful to determine and delineate fistula formation into the rectum or vagina ⁷

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

1. AP with full bladder for demonstration of the presence or absence of VUR.

2. Both obliques to demonstrate bilateral vesicoureteric junctions.

3. Post-void film to check for a ureterocele.

VCUG/MCU vs RUG/ASU

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) ³.