Indications
Pediatric:
- Febrile urinary tract infection (UTI) — evaluate for VUR
- Posterior urethral valves (PUV) — boys; suspected on prenatal ultrasound
- Ureterocele evaluation
- Pre- and post-operative ureteral reimplantation
Adult:
- Neurogenic bladder evaluation (bladder capacity, compliance, outlet obstruction)
- Bladder outlet obstruction (BPH, urethral stricture — complement to RUG)
- Post-traumatic urethral evaluation
- Urinary fistula evaluation (vesicovaginal, vesicointestinal)
- Post-surgical bladder evaluation (cystoplasty, diversion)
Normal Anatomy and Landmarks
| Structure | Normal Finding |
|---|---|
| Bladder | Smooth, round to oval; capacity ~400 mL adult, variable in children |
| Bladder base | Smooth floor; impression from prostate (males) / uterus/vagina (females) |
| Bladder neck | Opens symmetrically during voiding; no residual narrowing |
| Posterior urethra (males) | Prostatic and membranous urethra; widest at prostatic urethra; narrowest at external sphincter |
| Anterior urethra (males) | Bulbar urethra (widest segment), penile urethra; no filling defects or narrowing |
| Female urethra | Short (3–4 cm); smooth; opens well during voiding |
| Ureters | Should NOT fill retrograde with contrast during filling or voiding (= vesicoureteral reflux) |
Vesicoureteral Reflux — Grading (International Classification)
| Grade | Description |
|---|---|
| I | Contrast refluxes into ureter only — does not reach renal pelvis |
| II | Reflux to renal pelvis; no calyceal distension; normal calyceal fornices |
| III | Mild to moderate calyceal distension; mild tortuosity of ureter |
| IV | Moderate to severe calyceal blunting; significant ureteral and pelvic distension and tortuosity |
| V | Severe hydronephrosis; intrarenal reflux; grossly tortuous ureter |
Reflux grade determines management. Grade I–III: usually managed conservatively with antibiotic prophylaxis; most resolve spontaneously. Grade IV–V: higher risk of renal scarring; surgical or endoscopic correction (STING procedure) often indicated. Always report highest grade of reflux, timing (filling vs. voiding), and whether reflux resolves on post-void imaging.
Key Findings
Posterior Urethral Valves (PUV)
The most common cause of severe obstructive uropathy in males. Type I (most common) — sail-like leaflets at the level of the verumontanum.
| VCUG Finding | Description |
|---|---|
| Dilated posterior urethra | Marked dilation of prostatic and membranous urethra proximal to valve level |
| Abrupt caliber change at valve | Transition from dilated posterior to normal caliber anterior urethra at verumontanum level |
| Trabeculated bladder | Thick-walled, irregular bladder from chronic outlet obstruction |
| High-grade VUR | Bilateral VUR grade IV–V common due to elevated bladder pressures |
| Bladder diverticula | Multiple small diverticula from detrusor hypertrophy |
PUV is a urological emergency in neonates with bilateral hydronephrosis on prenatal ultrasound. The VCUG finding of a dilated posterior urethra with abrupt narrowing at the verumontanum requires immediate urology consultation.
Neurogenic Bladder
| Pattern | Features |
|---|---|
| Spastic (UMN lesion) | Small, trabeculated "Christmas tree" bladder; high pressure; detrusor-sphincter dyssynergia |
| Atonic (LMN lesion) | Large, smooth, flaccid bladder; poor voiding; high residual volume |
| Pine tree bladder | Irregular, trabeculated; pseudodiverticula; from suprasacral spinal cord lesions |
Other Findings
| Finding | Description |
|---|---|
| Bladder diverticulum | Smooth, outpouching through bladder wall; fills and empties (vs. stool/gas); Hutch diverticulum near ureteral orifice |
| Ureterocele | Cobra-head sign (filling defect with lucent halo at ureterovesical junction); simple vs. ectopic (associated with duplex system) |
| Vesicovaginal fistula | Contrast fills vagina during bladder filling or voiding |
| Bladder carcinoma | Irregular filling defect; wall thickening (incidental finding — refer for cystoscopy) |
Reporting Checklist
- Bladder morphology: normal / trabeculated / diverticula / capacity (if measured)
- VUR: absent / present — grade (I–V) / unilateral or bilateral / filling or voiding phase / resolution on post-void
- Posterior urethra (males): normal caliber / dilated / abrupt transition (PUV)
- Anterior urethra: normal / stricture / filling defect
- Bladder neck: opens symmetrically / obstructed
- Post-void residual: documented if measured
- Ureterocele: absent / present — simple or ectopic
- Fistula: present / absent
- Catheter position confirmed intra-vesical before injection
Common Pitfalls
| Pitfall | How to Avoid |
|---|---|
| Missing VUR on filling phase only | Always obtain voiding images — reflux is commonly seen only during the voiding phase when bladder pressure is highest |
| Catheter balloon inflated in posterior urethra | Balloon must be deflated and catheter advanced into bladder before voiding phase — balloon in posterior urethra obscures urethral anatomy |
| Missing PUV on filling image | Posterior urethra must be imaged during active voiding — PUV not visible on filling images; lateral view during voiding is critical |
| False-positive reflux from excessive filling | Overfilling the bladder beyond capacity can force reflux in a patient without true VUR; fill to physiologic capacity |
| Missing high-grade reflux on post-void film | Persistent calyceal filling after voiding = contrast trapped in upper tract; always obtain post-void AP film |
Step-by-step fluoroscopy technique and systematic search patterns available in RadCall Pro.