Overview
Definition:
Posterior urethral valves (PUV) are congenital obstructions in the urethra of male infants, characterized by redundant folds of mucosa extending from the verumontanum to the bladder neck
They represent the most common cause of bladder outlet obstruction in male neonates.
Epidemiology:
PUV affects approximately 1 in 2,000 to 5,000 live male births
The incidence varies geographically and may be related to diagnostic practices
The severity of PUV is often inversely related to gestational age at diagnosis.
Clinical Significance:
Untreated PUV can lead to severe consequences including bilateral renal dysplasia, chronic kidney disease, recurrent urinary tract infections, bladder diverticula, vesicoureteral reflux (VUR), and pulmonary hypoplasia due to oligohydramnios
Early diagnosis and effective management are crucial to preserve renal function and prevent long-term sequelae.
Clinical Presentation
Symptoms:
Prenatal findings include hydronephrosis and a dilated bladder
Postnatal presentation may include a weak or spraying urinary stream
Difficulty initiating voiding
Incomplete bladder emptying
Recurrent urinary tract infections (UTIs), often presenting with fever and irritability
Abdominal distension due to a palpable bladder
Poor weight gain and failure to thrive in severe cases
Respiratory distress if pulmonary hypoplasia is present.
Signs:
Palpable distended bladder
In severe cases, ascites may be present
Renal insufficiency may be evident with signs of fluid overload
Absence of normal male genital anatomy may suggest associated syndromes
Persistent urinary dribbling.
Diagnostic Criteria:
Diagnosis is typically made based on characteristic imaging findings and confirmed by cystourethroscopy
Key diagnostic findings include a distended bladder, thickened bladder wall, dilated posterior urethra, and often VUR
The presence of abnormal mucosal folds at the prostatic urethra is the defining feature of PUV.
Diagnostic Approach
History Taking:
Detailed antenatal history is essential, looking for maternal ultrasound findings of hydronephrosis, oligohydramnios, or a distended bladder
Postnatal history should focus on voiding patterns, presence of UTIs, and overall infant well-being
Inquire about family history of urological anomalies.
Physical Examination:
Careful abdominal examination for bladder distension
Genital examination to assess for hypospadias, undescended testes, or other anomalies
Assess for signs of dehydration or fluid overload
Assess respiratory status in neonates.
Investigations:
Antenatal ultrasound: Detects hydronephrosis, dilated bladder, and oligohydramnios
Postnatal ultrasound: Confirms bladder distension, bladder wall thickening, hydronephrosis, and may suggest urethral dilation
Voiding Cystourethrogram (VCUG): The gold standard for diagnosis, showing dilated posterior urethra, trabeculated bladder, VUR, and the characteristic linear defect of the valve
Renal function tests: Serum creatinine and electrolytes to assess renal function
Urinalysis and urine culture: To detect and manage UTIs.
Differential Diagnosis:
Other causes of bladder outlet obstruction in infants include posterior urethral stricture, prune belly syndrome, cloacal anomalies, and dysfunctional voiding
Differentiating features include the specific anatomical location and appearance of the obstruction.
Management
Initial Management:
Immediate management focuses on decompression of the bladder, often via a Foley catheter if feasible, or a suprapubic catheter if urethral access is difficult
Antibiotics are administered for UTIs.
Surgical Management:
The definitive treatment is transurethral ablation of the posterior urethral valves
This is typically performed using a cystoscope with an appropriate resectoscope or hook electrode
The goal is to transect or fulgurate the obstructing valve leaflets
The procedure is usually performed as early as possible, ideally within the first few days of life, to prevent irreversible renal damage
The adequacy of valve ablation is confirmed by VCUG post-operatively.
Supportive Care:
Post-operative care includes close monitoring of urine output, pain management, and antibiotics if indicated
Long-term follow-up is crucial to monitor for potential complications such as bladder dysfunction, recurrent UTIs, and persistent renal impairment.
Indications:
The primary indication for ablation is confirmed diagnosis of posterior urethral valves
Management decisions are guided by the severity of obstruction and its impact on renal function
Even mild PUV warrants treatment to prevent long-term complications.
Complications
Early Complications:
Bleeding from the urethra
Urinary tract infection
Urethral injury or stricture formation
Transient incontinence
Incomplete ablation requiring re-intervention.
Late Complications:
Persistent or recurrent VUR
Bladder dysfunction, including detrusor underactivity or overactivity leading to poor emptying and recurrent UTIs
Upper tract calculi formation
Chronic kidney disease and end-stage renal disease
Erectile dysfunction in adolescents and adults
Urethral stricture formation, particularly at the site of ablation.
Prevention Strategies:
Meticulous surgical technique during ablation to minimize trauma to the urethra and bladder neck
Prompt and aggressive management of UTIs
Regular follow-up to monitor for VUR and bladder dysfunction
Early identification and management of renal impairment.
Prognosis
Factors Affecting Prognosis:
The most significant factor influencing prognosis is the degree of renal dysplasia present at birth
Early diagnosis and treatment are crucial
The presence and severity of VUR also impact long-term renal outcomes
The development of bladder dysfunction can lead to progressive renal damage.
Outcomes:
With prompt and effective treatment, many children with PUV can achieve normal renal function and a satisfactory quality of life
However, a significant proportion will develop chronic kidney disease, requiring ongoing medical management and surveillance
Long-term bladder management may be necessary for some patients.
Follow Up:
Long-term follow-up is essential and should include regular renal function tests, serial ultrasounds of the kidneys and bladder, and periodic VCUGs to assess for VUR and bladder emptying
Uroflowmetry and post-void residual urine measurements are important for evaluating bladder function
Patients should be monitored into adulthood.
Key Points
Exam Focus:
PUV is a congenital bladder outlet obstruction in males
Key findings on VCUG include dilated posterior urethra, trabeculated bladder, and often VUR
Transurethral ablation is the definitive treatment
Renal dysplasia is the primary determinant of long-term prognosis.
Clinical Pearls:
Always consider PUV in male infants with unexplained hydronephrosis, urinary dribbling, or UTIs
Early intervention is critical to preserve renal function
Post-operative bladder dysfunction is common and requires careful monitoring and management
Consider associated anomalies, especially VUR and renal dysplasia.
Common Mistakes:
Delaying diagnosis or treatment can lead to irreversible renal damage
Incomplete ablation requiring repeat procedures
Neglecting to evaluate for VUR or bladder dysfunction post-ablation
Failure to implement long-term follow-up protocols for renal and bladder function.