Voiding Cystourethrogram (VCUG)
A VCUG is a fluoroscopic imaging technique that evaluates the bladder and urethra during filling and emptying, allowing assessment of both anatomical and functional aspects of the urinary tract. 1, 2
Procedure Overview
- Contrast is instilled into the bladder via a Foley catheter
- Images are taken in the upright position at:
- Rest
- Strain
- During voiding
- Multiple filling-voiding cycles are recommended for optimal diagnostic accuracy 3
Key Diagnostic Applications
Primary Uses
- Detection of vesicoureteral reflux (VUR) - gold standard test along with contrast-enhanced voiding urosonography 2
- Evaluation of urinary dysfunction
- Assessment of urethral and bladder anatomy
- Post-urinary tract surgery follow-up 2
Specific Findings VCUG Can Detect
- Cystocele (bladder extending below the pubic symphysis) 1
- Urethral angle changes and hypermobility 1
- Urethral diverticula during voiding 1
- Voiding dysfunction indicators:
- Funneling or involuntary urine leakage during straining
- Trabeculated bladder
- Large post-void residual
- Urethral narrowing with/without upstream dilation 1
Advantages of VCUG
- Performed in physiologic upright position
- Provides focused imaging of bladder and urethra during active voiding
- Can serve as initial imaging test for urinary dysfunction when clinically indicated 1
- Allows objective measurement of changes in cystocele height and urethral angle after surgical repair 1
Limitations
- Limited to anterior compartment structures (bladder and urethra) 1
- May show lower prevalence and degree of urethral hypermobility and cystoceles compared to MR defecography 1
- In severe voiding dysfunction, the urethra may not opacify, limiting evaluation 1
- Involves radiation exposure (though typically minimal with modern equipment) 2
Clinical Importance of Standardized Protocol
- The American Academy of Pediatrics Sections on Urology and Radiology published a standardized VCUG protocol in 2016 4
- Multiple filling-voiding cycles are recommended as 21.2% of VUR cases may be missed with a single cycle 3
- Important parameters to report include:
- VUR grade
- Volume at which reflux occurs
- Timing of reflux (filling vs. voiding)
- Post-void residual volume 5
Alternative Imaging Modalities
- For comprehensive pelvic floor assessment, MR defecography provides evaluation of all pelvic floor compartments 1
- In pediatric patients, contrast-enhanced voiding urosonography (VUS) is strongly recommended as a non-radiating alternative when possible 2
VCUG remains an essential diagnostic tool for evaluating urinary tract disorders, particularly when focused assessment of the bladder and urethra is needed during active voiding.