What are the indications, technique, contraindications, and alternatives for a vesicoureteral cystourethrogram?

Voiding Cystourethrogram (VCUG): Indications, Technique, Contraindications, and Alternatives

VCUG remains the gold standard for diagnosing vesicoureteral reflux (VUR) because it allows precise grading of reflux and detailed assessment of bladder and urethral anatomy in a single examination, despite concerns about radiation exposure. 1

Indications

Primary Indications for VCUG

• Initial diagnosis of VUR in children aged 2-24 months presenting with first febrile UTI, particularly when renal ultrasound shows hydronephrosis, scarring, or findings suggesting high-grade VUR or obstructive uropathy 1, 2

• Atypical or recurrent febrile UTI at any age, where VCUG is usually appropriate for initial imaging 1

• Prenatal hydronephrosis detected on ultrasound, though VCUG should be delayed at least 48-72 hours after birth to avoid false-positive results 2

• Neurogenic bladder (particularly myelomeningocele patients), where video-urodynamic studies or VCUG should be performed by 3 months of age to detect secondary VUR and prevent renal deterioration 1, 3

• Suspected posterior urethral valves in male infants, where VCUG provides critical visualization of the posterior urethra 1, 2

• Follow-up imaging for established VUR, recommended by the American Urological Association at 12-24 month intervals, with longer intervals for patients with higher grades (III-V), bladder/bowel dysfunction, or older age 1

Age-Specific Considerations

• Children <2 months: Ultrasound of kidneys and bladder is usually the first-line study, with VCUG reserved for abnormal findings 1

• Children >6 years with first febrile UTI: The likelihood of detecting previously unknown renal anomalies is low, and routine imaging may not be necessary unless there are atypical features 1

Technique

Standardized Protocol Requirements

A standardized protocol must be followed when performing VCUG to ensure diagnostic accuracy and minimize radiation exposure. 1, 2, 4

Equipment and Setup

• Fluoroscopy unit with recording capabilities 2
• Sterile catheterization kit with appropriately sized Foley catheter 2
• Contrast medium, sterile drapes, and gloves 2

Procedural Steps

1. Patient positioning: Place patient supine on fluoroscopy table 2

2. Catheterization: Insert appropriately sized Foley catheter using sterile technique 2

3. Bladder filling: Fill bladder with contrast under gravity at approximately 100 cm above the table 2

4. Cyclic imaging: Perform at least 2 filling-voiding cycles to detect intermittent VUR, as 21.2% of reflux cases are diagnosed only after an initial negative cycle, with 69.2% of these being dilating (clinically significant) reflux 5, 4

5. Voiding images: Obtain images during voiding to assess bladder emptying, urethral anatomy, and reflux during micturition 2, 6

6. Special attention in males: Carefully visualize the posterior urethra to detect posterior urethral valves 1, 2

Radiation Dose Optimization

• Cyclic studies performed in younger children actually result in lower median radiation doses (2.15 microGy m² vs 4.41 microGy m²) compared to single-cycle studies, likely due to more efficient technique 5

• Simplified protocols using only full-bladder and post-void images show 87.2-100% sensitivity and specificity for detecting reflux while significantly reducing radiation exposure 7

Contraindications

Absolute Contraindications

• Active urinary tract infection: VCUG should be deferred until after symptom resolution and completion of antibiotic therapy 8

• Acute pyelonephritis: Performing VCUG during an active infection episode is not recommended 8

Relative Contraindications

• Severe urethral trauma: Alternative imaging should be considered

• Known severe contrast allergy: Though iodinated contrast is not absorbed systemically from the bladder in significant amounts

Timing Considerations

• Newborns with antenatal hydronephrosis: Wait at least 48-72 hours after birth to avoid false-positive results 2

• Post-UTI timing: Perform after infection has resolved and antibiotic course completed 8

Alternatives to VCUG

Contrast-Enhanced Voiding Urosonography (ceVUS)

ceVUS is the primary alternative to VCUG, with comparable diagnostic accuracy and no ionizing radiation. 1, 6

• Sensitivity and specificity: 80-100% and 77.5-98%, respectively, with diagnostic accuracy of 78-96% compared to fluoroscopic VCUG 1

• Advantages: Some studies suggest ceVUS is more sensitive than VCUG for detecting dilated VUR, particularly when using transperineal approach for improved bladder and urethral evaluation 1

• 3D/4D techniques: Advanced ultrasound techniques with ceVUS result in greater detection of reflux compared to conventional VCUG 1

• European Society of Paediatric Radiology recommendation: Strongly recommends ceVUS as a non-radiating technique whenever indicated and possible 6

• Current guideline status: European Association of Urology gives ceVUS a "weak" recommendation as an alternative to VCUG for VUR diagnosis 1

Nuclear Medicine Cystography

• Useful for follow-up imaging of established VUR, recommended at 12-24 month intervals 1

• Lower radiation dose than VCUG but cannot grade reflux as precisely and provides limited anatomical detail 1

• Primary evidence supporting nuclear cystography is generally older than other modalities 1

Magnetic Resonance Urography (MRU)

• Suggested as a safer alternative for follow-up imaging of VUR causing renal scarring, particularly in children requiring serial studies 1

• Not appropriate for initial VUR diagnosis due to cost, need for sedation in young children, and inability to assess dynamic voiding

DMSA Renal Scan

• Not an alternative to VCUG for diagnosing VUR, but complementary for detecting renal scarring and differential kidney function 1

• Considered the best nuclear agent for visualizing cortical tissue 1

• May be appropriate for follow-up after febrile UTI or when renal ultrasound is abnormal 1

Critical Pitfalls to Avoid

Technical Pitfalls

• Single-cycle studies in young children: Performing only one filling-voiding cycle misses 21.2% of VUR cases; younger children who cannot control voiding require cyclic cystography 5, 4

• Inadequate visualization of male posterior urethra: May miss posterior urethral valves, which require careful attention during voiding phase 1, 2

• Premature VCUG in newborns: Performing before 48-72 hours of life increases false-positive rates 2

Clinical Decision Pitfalls

• Delaying VCUG beyond 3 months in neurogenic bladder: Early identification of hostile bladder patterns allows timely intervention with clean intermittent catheterization and anticholinergics, preventing irreversible bladder dysfunction 3

• Relying on ultrasound alone to exclude VUR: Normal postnatal ultrasound does not exclude reflux; VUR risk may be as high as 25% even with mildly dilated or non-dilated collecting systems 3

• Performing VCUG during active infection: Increases risk of bacteremia and may yield false-positive results for reflux 8

Infection Risk

• Iatrogenic UTI occurs in approximately 2% of VCUGs performed for antenatal hydronephrosis evaluation 2

• Consider prophylactic antibiotics in high-risk patients, though routine prophylaxis remains controversial 2