Congenital condition with obstructing leaflet or membrane at the posterior urethra.
Historically associated with significant mortality – now often treated in infancy but resulting high rates of chronic renal failure.
Incidence of 1 in 10 000 in NSW study.
Aetiology
3 types originally described by Young:
Type 1 (95 %) – hypertrophied variant of inferior urethral crest – leaflets arising from veru, proceeding anteriorly and fusing in midline just proximal to external sphincter
Type 2 – may not exist – arising from veru extending posteriorly to bladder neck
Type 3 – annular ring similar to a urethral stricture (no association with veru)
Pathophysiology
Valvular obstruction develops at about 7 weeks – result of abnormal embryogenesis at the confluence of the mesonephric duct and the urogenital sinus
Consequent urinary tract dilation may be appreciable on ultrasound at 14 weeks gestation.
Early outflow obstruction leads to excess collagen deposition in developing bladder, with or without renal hypoplasia/dysplasia.
The long term morbidity and renal failure associated with PUV is usually related to bladder dysfunction (high voiding pressures but often poor emptying), thought to be secondary to embryological impact (given often persists despite prompt treatment for newborn).
Prediction of long term outcomes difficult and all children need surveillance long term.
Pathological effects of PUV:
- Lung – pulmonary hypoplasia from oligohydramnios
- Kidney – initial insult often reversible with relief of obstruction, but ongoing progressive renal dysfunction with bladder damage
- Bladder – poorly compliant, hypercontractile bladder with poor sensation
- Ureter – poorly contractile and often permanently dilated
Presentation
Vast majority are detected antenatally with bilateral hydronephrosis on antenatal scan.
Despite the embryological failure occurring about 7 weeks, dilation not visible on scan until 15 weeks or so.
Earlier detection, i.e. less than 20 weeks gestation, and oligohydramnios (with subsequent pulmonary hypoplasia), are predictors of poorer outcome
DDx – urethral atresia, bilateral VUJ, Prune-Belly
Neonatally:
- Urinary symptoms – poor flow, palpable bladder, urinary ascites
- Systemic symptoms from renal failure – failure to thrive, listlessness, poor feeding
As infants:
- Often present with UTI
- Classically poor growth, renal failure and gram negative sepsis were presentations (less now with antenatal ultrasound)
Older children:
- Investigation of renal failure, voiding symptoms or investigation of enuresis
VURD syndrome – vesicoureteric reflux and dysplasia – high grade VUR on one side with an ipsilateral poorly functioning kidney, and a normal contra-lateral side – “pop-off” mechanism seems to provide more favourable outcome
Investigations
Antenatal ultrasound – “keyhole sign” with distended bladder and usually bilateral collecting system dilation
Postnatal ultrasound – upper tract dilation (sometimes unilateral), perinephric urinoma, bladder wall thickening, posterior urethral dilation
MCUG – ureteric reflux (often unilateral), grossly dilated posterior urethra with clear transition point to anterior urethra, thickened hypertrophied bladder neck, trabeculated bladder
Bloods – renal function and electrolytes (NB first 48 hours bloods may reflect mothers)
Management
Antenatally detected:
- Counselling and consideration of termination
- Vesico-amniotic shunting (in utero surgery) – no consensus on efficacy, bespoke
- Prepare for delivery in appropriate centre
Neonatal management:
- Drain the bladder – 5 or 6 fr feeding tube (SPC alternative, may be tricky with thick bladder)
- Stabilise medically
- Renal input
- Watch for post-obstructive diuresis
- Other issues – e.g. pulmonary hypoplasia (most common cause of mortality)
- Confirm the diagnosis – ultrasound and MCUG (without catheter)
- Consider complications i.e. urinomas which may need to be drained
Surgical management:
- Once medically stable, and creatinine has plateaued
- Resection or ablation of the valves through paediatric 9 fr resectocope – cold knife or loop/bugbee – 5/7/12 or 4/8
- Alternate is vesicostomy if babies too small/premature for resection
Other considerations:
- Antibiotic prophylaxis
- Circumcision for prophylaxis
- Re-look cystoscopy / MCUG at 3 months – can do circumcision in this sitting
- VUR often settles after treatment of the valve – if doesn’t settle, reimplanting in to high pressure bladders is problematic
- Long term follow up urologically and with renal
Long term follow up valve bladder and renal function. Eventually may require dialysis, transplant, intermittent self catheterisation, etc. Expect delays in toilet training.
Prognostic features
| Poorer prognosis: | Better prognosis: |
| · Earlier antenatal diagnosis < 20 weeks
· Oligohydramnios on antenatal scan · Diagnosis as neonate · Nadir creatinine as neonate and at 1 year old · Bilateral VUR · Proteinuria as child · Poorly compliant bladder on UDS as child |
· VURD syndrome / pop-off phenomenon
· Later presentation in childhood
|