A male neonate presents with a poor urinary stream and a palpably distended bladder. Antenatal scans had shown bilateral hydronephrosis and oligohydramnios. Ultrasound shows a thick-walled trabeculated bladder with bilateral hydroureteronephrosis. What is the single most appropriate investigation to establish the diagnosis?

• A Uroflowmetry
• B DMSA scan
• C Intravenous urogram
• D Micturating cystourethrogram ✓

Explanation

The presentation is classic for posterior urethral valves, the commonest cause of lower urinary tract obstruction in male infants. The diagnostic study is a micturating cystourethrogram, which shows a dilated posterior urethra with abrupt calibre change at the level of the valves, along with a trabeculated bladder and reflux. Ultrasound suggests obstruction but cannot visualise the valves. DMSA assesses cortical damage only, and uroflowmetry is impossible to interpret in a neonate.

Reference: Campbell-Walsh Urology, 12th ed.

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Written and medically reviewed by the StethoPrep medical team.