Basics
Description
A posterior urethral valve (PUV) is an embryologic remnant of tissue in the urethra that causes obstruction of the lower urinary tract during fetal development; this obstruction results in short-and long-term structural abnormalities and physiologic dysfunction in the genitourinary system (kidney, ureter, bladder, and urethra).
Epidemiology
- Most common cause of lower urinary tract obstruction in males
- The incidence is estimated to be between 1:3,000 and 1:8,000 live male births.
- Approximately 24 " 45% of children born with PUV will exhibit renal insufficiency during childhood.
- PUV accounts for up to 17% of the cases of children with end-stage renal failure.
Risk Factors
Genetics
- Majority of cases are isolated and occur sporadically.
- Rarely, cases have been reported in siblings.
Pathophysiology
- Multiple theories exist as to the embryologic origin of PUV.
- Male urethral development is usually complete by 14 weeks ' gestation; PUV formation is presumed to occur prior to this point.
- Possible embryologic origin of PUVs include (1) presence of an obstructing membrane in the posterior urethra, (2) overgrowth or abnormal folding during normal urethral development, (3) abnormal integration of the Wolffian ducts into urethral development, or (4) abnormal persistence of the urogenital membrane.
- PUVs exist in a spectrum of severity, likely related to the timing and degree of obstruction during development.
- The valve is a leaflet or membrane of thin connective tissue that extends from the anterior urethral lip to the verumontanum posteriorly, obstructing the normal flow of urine through the urethra. This results in an elongated urethra and upstream dilation in the urinary system.
- PUVs are commonly associated with intrinsic renal dysplasia. Studies have demonstrated that dysplastic renal parenchyma at time of birth is permanent.
- Commonly associated pathophysiologic findings in children with PUV include (1) hydroureteronephrosis, (2) dilated bladder with trabeculations and/or diverticulum, and (3) vesicoureteral reflux.
- PUVs may result in early or late bladder dysfunction with decreased compliance and increased voiding pressure that affect both the storage and expulsion of urine as well as expose the upper tract of the urinary system to increased pressure, which leads to worsening renal function over time.
Commonly Associated Conditions
- Genitourinary: hydroureteronephrosis, vesicoureteral reflux, bladder wall thickening and diverticulum, obstructive urinary symptoms, urinary ascites in cases of bladder rupture, perirenal urinoma in cases of renal collecting system rupture
- Varying degrees of renal insufficiency may also be present in patients from birth through adulthood.
- PUV has been associated with other congenital anomalies of the genitourinary tract: prune belly syndrome, imperforate anus, and congenital heart disease.
Diagnosis
History
- PUVs generally present in four ways:
- Fetal diagnoses by ultrasound (US)
- Neonates with respiratory distress, abdominal distension, metabolic abnormalities
- Infants with febrile UTI/sepsis/poor urinary stream
- Delayed presentation in children with UTI or voiding difficulties
- Fetal presentation (diagnosis on ultrasound)
- Dilated, thick-walled bladder
- Bilateral and in some cases unilateral hydroureteronephrosis
- "Keyhole sign " : dilated posterior urethra at the base of the bladder
- Decreased amniotic fluid/oligohydramnios
- Neonatal presentation
- Tachypnea/respiratory distress
- Poor feeding/failure to thrive/abdominal distension
- Lethargy/acidosis and azotemia
- Cardiovascular compromise and arrhythmia/hyperkalemia
- Delayed or infrequent voiding
- Infant/toddler presentation
- Failure to thrive
- Abdominal distension
- Fever of unknown origin
- Febrile UTI
- Urosepsis
- Delayed presentation
- UTI
- Abnormal or weak urinary stream
- Urinary complaints such as hesitancy, incomplete emptying, dysuria, straining
- Urinary incontinence, sometimes with palpable bladder
- Polyuria and urinary frequency secondary to renal concentrating defect
Physical Exam
A palpable bladder is the most common physical exam finding. In infants, abdominal distension may be present from severe bladder distension and hydroureteronephrosis or urinary ascites. Hyperpigmented perigenital skin may also be noted from severe incontinence and urine irritation of the skin.
Diagnostic Tests & Interpretation
Lab
- Urinalysis: UTI, proteinuria, low specific gravity
- Metabolic panel: elevated creatinine, azotemia, acidosis, hyperkalemia, hyponatremia, renal tubular acidosis (RTA) (type IV)
- CBC: elevated WBC in face of UTI; anemia in renal insufficiency
Imaging
- Renal and bladder US: dilation of posterior urethra (keyhole sign), distended/thick-walled bladder with possible diverticuli, hydroureteronephrosis, echogenic or dysplastic renal parenchyma
- Voiding cystourethrogram (VCUG): diagnostic study. Shows dilated posterior urethra with abnormal runoff of urine in the posterior urethra, capacious bladder with possible trabeculations or diverticulum, vesicoureteral reflux
- KUB: ground-glass appearance in cases of bladder rupture and urinary ascites
Diagnostic Procedures/Other
Operative cystoscopy: visual evaluation of urethra, and bladder provides definitive diagnosis
Differential Diagnosis
- Prune belly syndrome
- Vesicoureteral reflux
- Urethral stricture disease (congenital and acquired)
- Anterior urethral valves
- Urethral atresia
- Primary ureterovesical junction (UVJ) obstruction (megaureter)
- Severe voiding dysfunction
- Polyuria
- Megacystis " megaureter syndrome
- UTI
Treatment
General Measures
Supportive
- Insertion of a urethral catheter or feeding tube in the neonate to bypass obstruction
- Confirm placement of catheter in the bladder by ultrasound, as small catheters may coil in the posterior urethra and drain some urine, giving the false impression of being located within the bladder.
- Correction of electrolyte abnormalities with careful observation for postobstructive diuresis
- Monitoring of fluid status
- Antibiotics for any evidence of a UTI; treat UTI as complex
- Consultation with a pediatric urologist
Surgery/Other Procedures
- Resection of the valve (ablation) is the definitive treatment of the primary lesion; typically performed cystoscopically (through the urethra).
- In utero drainage of the fetal bladder is performed at some centers. Typically performed on patients with good urine parameters to mitigate pulmonary dysfunction from oligohydramnios. No significant improvement found in long-term renal outcome compared to valve ablation after delivery.
- If the infant is premature or the urethra is too small for the cystoscope, a vesicostomy may be required.
- Supravesical diversion (of the kidney or ureter) is sometimes performed in select patients who fail to improve after bladder decompression; associated with poorer long-term bladder function.
- Following valve ablation, the posterior urethra should have decreasing dilation on VCUG. Improvement in hydroureteronephrosis and vesicoureteral reflux (if it resolves spontaneously) will occur more slowly.
Ongoing Care
Follow-up Recommendations
- Lifelong follow-up is required, as renal insufficiency and bladder dysfunction can occur at any time during infancy, childhood, puberty, or adulthood.
- Pediatric urology follow-up is required for future reconstructive procedures and monitoring of bladder function, reflux, and hydronephrosis.
- Pediatric nephrology follow-up is recommended for long-term monitoring and mitigation of renal dysfunction.
- Delayed urethral obstruction is possible due to urethral stricture or incomplete initial valve resection.
- Patients with persistent incontinence, those who develop incontinence, or those with incomplete bladder emptying may require urodynamic evaluation to evaluate the bladder function/physiology and tailor therapy.
Patient Monitoring
- Careful follow-up through adulthood should be performed.
- Visits should include the following:
- Imaging (US) to evaluate renal, ureteral, and bladder anatomy
- Assessment of bladder function (incontinence, UTI, incomplete emptying)
- Blood pressure monitoring
- Serial creatinine
- Urinalyses to asses for proteinuria
- Assessment of overall linear growth
Prognosis
- Oligohydramnios during pregnancy is a predictor of worse long-term renal outcomes. The earlier it occurs during pregnancy, typically more severe issues are noted.
- Pulmonary hypoplasia (with concomitant renal dysfunction) accounts for the highest mortality in infants.
- Overall, the prognosis for severe PUV has improved over the past few decades, owing to earlier recognition and improved management of pulmonary hypoplasia and fluid and metabolic derangements.
- The rate of improvement in renal function after the valvular obstruction is relieved is more indicative of prognosis than initial creatinine at presentation.
- A creatinine level of <0.8 mg/dL around 1 year of age has the best long-term renal prognosis in patients treated in infancy.
- A nadir creatinine level <1.0 mg/dL may still be associated with eventual renal failure as the child ages; monitoring is warranted in all cases.
- Patient may progress to renal failure and require renal transplantation at any point during childhood or adulthood. An abnormal creatinine at 2 years of age carries higher likelihood of end-stage renal progression during adolescence or puberty.
- Children who develop proteinuria have bilateral renal dysplasia and/or bladder dysfunction and are more likely to eventually develop renal insufficiency and hypertension.
Complications
- Intrauterine oligohydramnios in severe cases may result in Potter syndrome and pulmonary hypoplasia.
- Renal dysplasia and parenchymal damage may lead to progressive renal failure, including associated issues, such as anemia, acidosis, fluid and electrolyte abnormalities, and failure to thrive.
- UTIs and vesicoureteral reflux are commonly associated with PUV.
- Urinary incontinence may result from overactive bladder (uninhibited contractions), incomplete emptying (bladder noncompliance), and polyuria.
Additional Reading
- Chertin B, Cozzi D, Puri P. Long-term results of primary avulsion of posterior urethral valves using a Fogarty balloon catheter. J Urol. 2002;168(4):1841 " 1843. [View Abstract]
- Eckoldt F, Heling KS, Woderich R, et al. Posterior urethral valves: prenatal diagnostic signs and outcome. Urol Int. 2004;73(4):296 " 301. [View Abstract]
- Hodges SJ, Patel B, McLorie G, et al. Posterior urethral valves. ScientificWorldJournal. 2009;9:1119 " 1126. [View Abstract]
- Holmes N, Harrison MR, Baskin LS. Fetal surgery for posterior urethral valves: long-term postnatal outcomes. Pediatrics. 2001;108(1):E7. [View Abstract]
- Krishnan A, de Souza A, Konijeti R, et al. The anatomy and embryology of posterior urethral valves. J Urol. 2006;175(4):1214 " 1220. [View Abstract]
- Radhakrishnan J. Obstructive uropathy in the newborn. Clin Perinatol. 1990;17(1):215 " 239. [View Abstract]
- Roth KS, Carter WH Jr, Chan JC. Obstructive nephropathy in children: long-term progression after relief of posterior urethral valve. Pediatrics. 2001;107(5):1004 " 1010. [View Abstract]
- Yiee J, Wilcox D. Management of fetal hydronephrosis. Pediatr Nephrol. 2008;23(3):347 " 353. [View Abstract]
Codes
ICD09
- 753.8 Other specified anomalies of bladder and urethra
- 753.6 Atresia and stenosis of urethra and bladder neck
- 593.89 Other specified disorders of kidney and ureter
- 591 Hydronephrosis
- 593.70 Vesicoureteral reflux unspecified or without reflux nephropathy
ICD10
- Q64.2 Congenital posterior urethral valves
- Q64.39 Other atresia and stenosis of urethra and bladder neck
- N28.89 Other specified disorders of kidney and ureter
- N13.30 Unspecified hydronephrosis
- N13.70 Vesicoureteral-reflux, unspecified
SNOMED
- 253900005 Congenital posterior urethral valves (disorder)
- 253901009 Congenital urethral posterior valvular stricture (disorder)
- 42399005 renal failure syndrome (disorder)
- 43064006 Hydronephrosis (disorder)
- 197811007 vesicoureteric reflux (disorder)
FAQ
- Q: What can be done for children with long-term bladder dysfunction and incontinence?
- A: Patients should be on a comprehensive bowel and bladder regimen due to increased incidence of voiding dysfunction. Additionally, more advance bladder management including intermittent catheterization and pharmacotherapy may be required.
- Q: Are patients with PUVs good candidates for renal transplantation?
- A: PUV patients have a 5-year transplanted kidney survival rate of around 50%, likely resulting from poor bladder function. Therefore, aggressive bladder management and long-term follow-up are prudent in these patients.
- Q: What is "valve-bladder syndrome " ?
- A: A valve-bladder is a bladder that is noncompliant and stores urine at high pressure, increasing the incidence of renal damage. It is thought to occur in approximately 20% of PUV patients.
- Q: What is VURD syndrome in PUV patients?
- A: Vesicoureteral reflux and unilateral renal dysplasia (VURD) occurs in 13% of PUV patients. A single renal unit has renal dysplasia and severe reflux, thereby allowing the high bladder pressures in PUV to be transmitted to a single kidney, sparing the contralateral (nonrefluxing) kidney from damage.