Posterior urethral valves — newborn management structured clinical encounter

Task 1 — Risk-stratify and recognise the diagnosis (4 minutes)

Read the antenatal data and the newborn examination. State the leading diagnosis and the risk band, and justify your reasoning from the APD values, the bladder, the laterality, the sex and the oligohydramnios. The expected answer is posterior urethral valves in the critical to high-risk band: the male sex, bilateral APD well above 10 mm, the thick-walled distended bladder, and the oligohydramnios together make posterior urethral valves the leading diagnosis until proven otherwise. ^{[3] [7]}

Task 2 — Immediate management bundle (5 minutes)

Outline your actions in the first 72 hours: ultrasound timing, catheterisation, prophylaxis, baseline bloods, and specialist referral. The expected bundle is a renal ultrasound within 48 to 72 hours (or sooner given the palpable bladder); a urethral catheter to decompress the bladder; a prophylactic antibiotic (confirm agent and dose locally) pending exclusion of obstruction and reflux; baseline creatinine and electrolytes; and urgent paediatric urology referral for a voiding cystourethrogram to confirm the dilated posterior urethra and valve, then cystoscopic valve ablation. Maintain hydration and perfusion. ^{[3] [6]}

Task 3 — Imaging interpretation and functional testing (4 minutes)

The voiding cystourethrogram confirms a dilated posterior urethra with an obstructing valve. Explain what further functional imaging may be needed and why, and what the ultrasound would show in bilateral dysplasia. The expected answer is MAG3 renography for differential renal function once the infant is stable, and DMSA to map cortical damage and confirm dysplasia if the ultrasound shows echogenic, small kidneys with loss of corticomedullary differentiation. The functional imaging quantifies how much renal reserve remains and guides the long-term surveillance intensity. ^{[7] [1]}