Overview
Definition:
Posterior urethral valves (PUV) are congenital obstructions in the male urethra, located distal to the verumontanum, causing progressive bladder outlet obstruction and significant upper urinary tract dilatation
They are the most common cause of bladder outlet obstruction in male infants.
Epidemiology:
PUV affects approximately 1 in 5,000 to 1 in 8,000 live male births
The prevalence of severe renal damage and the need for long-term dialysis or transplantation is significant, making early diagnosis and management crucial.
Clinical Significance:
PUV is a critical diagnosis in neonatology and pediatric urology
It can lead to irreversible renal damage, chronic kidney disease, pulmonary hypoplasia due to oligohydramnios, and long-term voiding dysfunction if not managed promptly and effectively
Understanding prenatal hydronephrosis helps in early detection and intervention.
Prenatal Hydronephrosis
Detection:
Hydronephrosis is often detected on routine antenatal ultrasound scans, typically in the second trimester
Findings include dilated renal pelves, caliectasis, thickened bladder walls, and a dilated posterior urethra (the "keyhole" sign).
Oligohydramnios:
Severe obstruction can lead to oligohydramnios, which is associated with pulmonary hypoplasia and a poorer long-term prognosis due to pulmonary and renal insufficiency
Amniotic fluid index (AFI) is a key indicator.
Fetal Management Considerations:
Management decisions are based on the severity of hydronephrosis, presence of oligohydramnios, and fetal renal function
Vesicocentesis may be considered for therapeutic decompression in select cases, but its role is controversial
Fetal urinary shunting is rarely indicated and has limited success.
Clinical Presentation
Neonatal Symptoms:
Failure to thrive
Poor feeding
Irritability
Vomiting
Jaundice
Distended abdomen
Weak urinary stream
Intermittent urinary stream
Urinary retention.
Infant And Older Child Symptoms:
Recurrent urinary tract infections (UTIs)
Poor growth
Daytime and nocturnal enuresis
Urgency
Frequency
Straining to void
Abdominal pain
Incontinence.
Physical Examination Findings:
Palpable distended bladder
Palpable kidneys (if hydronephrotic)
In severe cases, signs of renal insufficiency
Meatal stenosis can sometimes be associated or mistaken for the obstruction.
Diagnostic Criteria:
Diagnosis is primarily confirmed by postnatal imaging and visualization during cystoscopy
Key findings include dilated prostatic urethra, thickened bladder wall, trabeculated bladder, and identifiable valves on cystourethroscopy.
Diagnostic Approach
History Taking:
Detailed antenatal history including ultrasound findings
Postnatal history of voiding pattern, UTIs, fever, and failure to thrive
Family history of urogenital anomalies.
Physical Examination:
Abdominal examination for distension, palpable bladder, or enlarged kidneys
Genital examination to assess meatus location and size
Assess overall growth and development.
Imaging Investigations:
Postnatal ultrasound is the first-line imaging, assessing renal size, echogenicity, pelvicalyceal dilatation, bladder wall thickness, and presence of dilated prostatic urethra
Voiding cystourethrogram (VCUG) is essential for definitive diagnosis and assessment of valve severity
Renal function tests (serum creatinine, BUN) are critical.
Differential Diagnosis:
Other causes of bladder outlet obstruction: meatal stenosis, prune belly syndrome, neuropathic bladder, cloacal malformations, dysfunctional voiding
Strictures in the urethra are less common as a congenital cause.
Management
Initial Management Neonates:
Immediate decompression via suprapubic catheterization or urethral catheterization if feasible
Management of fluid and electrolyte imbalances
Antibiotics for UTIs
Assess renal function and degree of hydronephrosis.
Surgical Management:
The definitive treatment is valve ablation via cystourethroscopy
This involves incising or resecting the obstructing valves using a cold-knife or electrocautery
This is typically performed as soon as the diagnosis is confirmed, often within the first few days of life
Post-operative management includes Foley catheter drainage for a short period.
Medical Management Post Ablation:
Antibiotic prophylaxis may be continued, especially if recurrent UTIs are a concern
Management of any residual bladder dysfunction is crucial
Long-term follow-up with regular renal function monitoring and uroflowmetry is essential.
Supportive Care:
Monitoring of urine output, renal function, and electrolyte balance
Nutritional support
Education for parents regarding the condition and long-term follow-up requirements
Management of UTIs with appropriate antibiotics.
Complications
Early Complications:
Bleeding from the urethra
Urethral injury during instrumentation
Recurrent UTIs
Persistent hydronephrosis or renal insufficiency
Bladder perforation
Bladder neck or urethral stricture formation.
Late Complications:
Chronic kidney disease (CKD)
End-stage renal disease (ESRD) requiring dialysis or transplantation
Pulmonary hypoplasia
Poor growth and development
Nocturnal enuresis and daytime incontinence
Bladder diverticula
Vesicoureteral reflux (VUR) can be a consequence or co-exist.
Prevention Strategies:
Prompt diagnosis and surgical ablation of valves
Careful surgical technique during ablation
Judicious use of antibiotics for UTIs
Long-term monitoring to detect and manage VUR or bladder dysfunction
Regular follow-up with pediatric nephrologists and urologists.
Prognosis
Factors Affecting Prognosis:
Severity of prenatal hydronephrosis
Presence and severity of oligohydramnios
Degree of renal dysplasia
Age at diagnosis and treatment
Development of significant VUR or chronic kidney disease
Pulmonary status at birth.
Outcomes:
With timely diagnosis and effective treatment, many boys can achieve normal renal function and satisfactory voiding
However, a significant proportion may develop chronic kidney disease or require long-term management for voiding dysfunction
Those with severe prenatal insults may have poorer outcomes.
Follow Up:
Lifelong follow-up is recommended
This includes regular renal function monitoring (serum creatinine, GFR), periodic ultrasounds, uroflowmetry, and assessment for UTIs
Management of bladder dysfunction may involve timed voiding, anticholinergic medications, or intermittent catheterization
Screening for VUR should be done post-ablation.
Key Points
Exam Focus:
PUV is the most common cause of congenital bladder outlet obstruction in males
Antenatal hydronephrosis and oligohydramnios are critical indicators
VCUG is the gold standard for diagnosis
Valve ablation is the primary treatment
Long-term renal function and voiding dysfunction are key concerns.
Clinical Pearls:
Always suspect PUV in a male infant with unexplained hydronephrosis or UTIs
The "keyhole" sign on fetal ultrasound is suggestive
Inadequate urinary stream is a red flag in infants and older children
Post-ablation, monitor for VUR and bladder compliance issues.
Common Mistakes:
Delaying diagnosis due to reliance solely on antenatal findings without postnatal confirmation
Inadequate assessment of renal function and degree of hydronephrosis
Insufficient follow-up leading to missed late complications like CKD or voiding dysfunction
Incorrect interpretation of VCUG findings.