Posterior Urethral Valves (PUV)
Summary
Posterior urethral valves (PUV) are congenital membranous folds in the posterior urethra that obstruct urinary outflow. It is the most common cause of bladder outlet obstruction in male infants and a leading cause of end-stage renal disease (ESRD) in children. PUV occurs only in males. It is often diagnosed antenatally on ultrasound (bilateral hydronephrosis, dilated bladder, "keyhole sign") or postnatally with poor urinary stream, palpable bladder, or urinary tract infection. Severe cases cause oligohydramnios, leading to pulmonary hypoplasia. Initial management involves bladder drainage (catheterisation), followed by cystoscopic valve ablation. Long-term follow-up is essential as many develop chronic kidney disease.
Key Facts
- Definition: Congenital membranous folds obstructing posterior urethra
- Sex: Males only
- Most Common: Cause of bladder outlet obstruction in boys
- Antenatal Ultrasound: "Keyhole sign" (dilated bladder + posterior urethra), Bilateral hydronephrosis
- Complications: CKD, Pulmonary hypoplasia, Vesicoureteric reflux
- Treatment: Catheterise → Cystoscopic valve ablation
Clinical Pearls
"Keyhole Sign": On antenatal USS, a dilated bladder with dilated posterior urethra looks like a keyhole — pathognomonic for PUV.
"Boys Only": PUV does not occur in females.
"Catheterise First": Initial management in a sick neonate is to drain the bladder via catheter.
"Long-Term Renal Follow-Up": Up to 30% of PUV patients develop ESRD despite treatment. Lifelong monitoring is essential.
Incidence
- 1 in 5,000-8,000 male live births
Demographics
- Males ONLY
- Often diagnosed antenatally
Associations
- Vesicoureteric reflux (50%)
- Renal dysplasia
- Oligohydramnios
Anatomy
- Membranous folds (valves) in the posterior urethra
- Obstruct urine outflow
Consequences of Obstruction
- Bladder distension and hypertrophy ("valve bladder")
- High pressure transmitted to ureters → Hydroureter, Hydronephrosis
- VUR (vesicoureteric reflux) in 50%
- Back pressure → Renal dysplasia and CKD
- Oligohydramnios → Pulmonary hypoplasia
Classification (Young's)
- Type I: Most common (95%); Folds arise from verumontanum
- Type II: Rare/disputed
- Type III: Membrane distal to verumontanum
Antenatal (Ultrasound Findings)
| Finding | Notes |
|---|---|
| Keyhole sign | Dilated bladder + Posterior urethra |
| Bilateral hydronephrosis | |
| Thick-walled bladder | |
| Oligohydramnios | Severe cases; Risk of pulmonary hypoplasia |
Postnatal
| Feature | Description |
|---|---|
| Poor urinary stream | Dribbling, Straining |
| Palpable bladder | |
| Abdominal distension | Large bladder |
| Failure to thrive | |
| UTI / Urosepsis | May be first presentation |
| Respiratory distress | If pulmonary hypoplasia |
Inspection
- Abdominal distension
- Palpable bladder
Palpation
- Suprapubic mass (distended bladder)
- Kidneys may be palpable
General
- Signs of renal failure
- Respiratory distress (if lung hypoplasia)
Imaging
| Modality | Findings |
|---|---|
| Antenatal USS | Keyhole sign, Hydronephrosis, Oligohydramnios |
| Postnatal USS | Thick-walled bladder, Hydronephrosis |
| MCUG (Micturating Cystourethrogram) | Gold standard; Shows dilated posterior urethra, Valve leaflets, VUR |
Renal Function
| Test | Notes |
|---|---|
| Serum creatinine | May be falsely low in neonate (reflects maternal) |
| Follow creatinine over days | True neonatal function after 48-72 hours |
| Electrolytes | Hyperkalaemia, Acidosis |
DMSA Scan
- Assess differential renal function and scarring
Management Approach
┌──────────────────────────────────────────────────────────┐
│ POSTERIOR URETHRAL VALVES MANAGEMENT │
├──────────────────────────────────────────────────────────┤
│ │
│ INITIAL (NEONATAL STABILISATION): │
│ • Catheterise bladder (6-8 Fr feeding tube) │
│ • Correct electrolytes and acidosis │
│ • IV fluids │
│ • Treat sepsis if present │
│ │
│ DEFINITIVE TREATMENT: │
│ • Cystoscopic Valve Ablation │
│ - Endoscopic incision/ablation of valves │
│ - Gold standard │
│ • Vesicostomy (if baby too small for cystoscopy) │
│ - Cutaneous diversion │
│ - Closed later │
│ │
│ LONG-TERM FOLLOW-UP (ESSENTIAL): │
│ • Monitor renal function (creatinine, eGFR) │
│ • Blood pressure monitoring │
│ • USS for hydronephrosis resolution │
│ • Bladder function assessment │
│ • Transition to adult nephrology/urology │
│ │
│ "VALVE BLADDER": │
│ • Bladder dysfunction persists in many │
│ • May need CIC (clean intermittent catheterisation) │
│ • Anticholinergics for overactivity │
│ │
└──────────────────────────────────────────────────────────┘
Antenatal/Perinatal
- Oligohydramnios → Pulmonary hypoplasia
- Perinatal death (severe cases)
Renal
- Chronic kidney disease (30% develop ESRD)
- Hypertension
- Proteinuria
Bladder
- Valve bladder: High pressure, Poor compliance
- Urinary incontinence
Good Prognostic Factors
- Normal amniotic fluid
- Normal renal function at 1 year
- Bilateral good kidneys on DMSA
Poor Prognostic Factors
- Oligohydramnios
- Pulmonary hypoplasia
- Elevated nadir creatinine (>1 mg/dL at 1 year)
- Bilateral renal dysplasia
Long-Term
- 30% develop ESRD
- Many need renal transplant
- Bladder dysfunction is lifelong in many
Key Guidelines
- BAPU: British Association of Paediatric Urologists
- EAU: Paediatric Urology Guidelines
Key Evidence
Nadir Creatinine
- Creatinine at 1 year is best predictor of long-term renal outcome
What Are Posterior Urethral Valves?
Posterior urethral valves (PUV) are small flaps of tissue in the tube that carries urine out of the bladder (the urethra). They block the flow of urine.
Who Gets It?
Only boys can have PUV. It is present from birth.
How is It Diagnosed?
It is often found on ultrasound during pregnancy (a "keyhole" shape in the bladder area) or after birth if the baby has a weak urine stream, infections, or other problems.
How is It Treated?
- First, a small tube (catheter) is placed in the bladder to drain the urine
- Then, keyhole surgery is done to remove the valves
What's the Long-Term Outlook?
Many children do well, but some develop kidney problems later in life. Regular check-ups with a kidney doctor (nephrologist) are very important.
Primary Guidelines
- British Association of Paediatric Urologists. PUV Guidelines.
- European Association of Urology. EAU Paediatric Urology Guidelines. 2023.
Key Studies
- Dinneen MD, Dhillon HK, Ward HC, et al. Antenatal diagnosis of posterior urethral valves. Br J Urol. 1993;72(3):364-369. PMID: 8220996