SN5
SHORT NOTE
5M
Define Posterior Urethral Valves. Describe its clinical features, investigations, management and pathophysiology.
Definition
- Posterior urethral valves (PUV) are abnormal obstructing membranous folds in the posterior urethra, and are the commonest cause of congenital lower urinary tract obstruction in male infants.
- The obstruction causes back-pressure damage to the entire urinary tract.
Clinical Features
- Antenatal — bilateral hydronephrosis, a distended bladder, and oligohydramnios on ultrasound (oligohydramnios → pulmonary hypoplasia).
- Newborn/infant — poor urinary stream/dribbling, a palpable bladder, failure to thrive, urinary tract infection, or renal failure.
- Older boys — voiding difficulty, incontinence, recurrent UTI.
Investigations
- Ultrasound — bilateral hydroureteronephrosis and a thick-walled, distended bladder.
- Micturating cystourethrogram (MCU) — the diagnostic test; shows a dilated posterior urethra above the valve (± VUR).
- Renal function and electrolytes.
Management
- Initial — bladder catheter drainage, and correction of fluid/electrolyte and acid-base disturbances; treat infection.
- Definitive — endoscopic valve ablation.
- Long-term follow-up for chronic kidney disease, bladder dysfunction and growth.
Pathophysiology
The obstructing valves raise pressure throughout the urinary tract, causing bladder hypertrophy, hydroureteronephrosis and, antenatally, reduced urine output → oligohydramnios and pulmonary hypoplasia (a cause of neonatal respiratory difficulty).
Prognosis
Outcome depends on the degree of renal damage already present at birth; despite valve ablation, a significant proportion develop chronic kidney disease and bladder dysfunction, so lifelong nephro-urological follow-up is essential.
Associated Problems
- Bladder dysfunction (thick-walled, poorly compliant bladder) often persists after valve ablation.
- Vesicoureteric reflux and recurrent UTIs; and, antenatally, pulmonary hypoplasia from oligohydramnios.
Commonest cause of bladder outlet obstruction in male infants.
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