A 1-day-old neonate with prenatally diagnosed hydronephrosis is evaluated. MCU (micturating cystourethrogram) shows an elongated dilated posterior urethra with a distinct narrowing at the distal end, and bladder wall thickening with trabeculations. The diagnosis is:

• A Ureteropelvic junction obstruction
• B Posterior urethral valves ✓
• C Vesicoureteric reflux grade V
• D Ureterocele

Explanation

Posterior urethral valves are the most common cause of bladder outlet obstruction in male neonates. MCU classically shows an elongated dilated posterior urethra with distal narrowing, giving a keyhole appearance, along with bladder trabeculation and thickening. UPJ obstruction shows isolated pelvicalyceal dilation without posterior urethral changes. Ureterocele appears as a filling defect at the bladder base. Vesicoureteric reflux shows retrograde filling of the ureter.

Reference: Coran's Pediatric Surgery, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.