TOACS FCPS Station · MCUG: Posterior Urethral Valves (PUV)

📷 Micturating Cystourethrogram (MCUG)

MCUG showing dilated posterior urethra, bladder trabeculation, and vesicoureteral reflux in posterior urethral valves

Figure 1 · MCUG · Posterior Urethral Valves

🔍 Key radiographic features:

✓ Dilated posterior urethra – “spinning top” or “wind sock” appearance
✓ Bladder trabeculation – irregular bladder wall from chronic obstruction
✓ Vesicoureteral reflux – contrast reflux into ureters (bilateral or unilateral)
✓ Narrowed membranous urethra – valve leaflets at the level of the verumontanum
✓ Thickened bladder wall – with diverticula or cellules

📋 Clinical scenario (examiner prompt)

A 2‑week‑old male infant presents with poor urinary stream, palpable bladder, and failure to thrive. Prenatal ultrasound showed bilateral hydronephrosis and a dilated bladder. A micturating cystourethrogram (MCUG) is performed. The image shows a dilated posterior urethra with bladder trabeculation and vesicoureteral reflux.

Poor stream Dilated posterior urethra Bladder trabeculation Hydronephrosis

🧑‍⚕️ Examiner tasks · TOACS

1. Identify the diagnosis from the MCUG and clinical context.

2. Describe the X‑ray findings (dilated posterior urethra, bladder trabeculation, VUR).

3. Explain the pathophysiology (congenital obstruction from urethral folds).

4. Discuss management (catheterization, valve ablation, renal protection).

⚠️ Key concept: Posterior urethral valves (PUV) are the most common cause of lower urinary tract obstruction in male infants. They cause bladder outlet obstruction, leading to bladder trabeculation, vesicoureteral reflux, hydronephrosis, and renal dysplasia. Valve ablation is the definitive treatment, with long‑term follow‑up for renal function and bladder dysfunction.

🎯 Expected answers (for examiners)

• Diagnosis: Posterior urethral valves (PUV)
• X‑ray findings: Dilated posterior urethra, bladder trabeculation, vesicoureteral reflux, thickened bladder wall
• Pathophysiology: Congenital mucosal folds in the posterior urethra (at verumontanum) → obstruction → bladder hypertrophy, VUR, renal dysplasia
• Management: Urinary catheterization (initial), endoscopic valve ablation, monitoring for bladder dysfunction and CKD

⚡ Quick FCPS‑style MCQ

The characteristic MCUG finding in a male infant with posterior urethral valves is:

A. Dilated posterior urethra with bladder trabeculation B. Prostatic urethral narrowing C. Normal urethral caliber with bladder diverticula D. Urethral duplication

Feature	Posterior Urethral Valves
Sex	Male only
In utero	Oligohydramnios, Potter facies
MCUG	Dilated posterior urethra, trabeculated bladder
Associated	VUR (50-70%), renal dysplasia
Treatment	Valve ablation, bladder training

🩻 TOACS FCPS Station · MCUG: Posterior Urethral Valves (PUV)

📷 Micturating Cystourethrogram (MCUG)

🧑‍⚕️ Examiner tasks · TOACS

📌 Topic summary ·