Posterior Urethral Valves (PUV) in Children
Understanding urinary obstruction in boys, its effects on the bladder and kidneys, and available treatment options.
Posterior Urethral Valves (PUV) in Children
Understanding urinary obstruction in boys, its effects on the bladder and kidneys, and available treatment options.
Overview
Posterior urethral valves (PUV) are a congenital condition affecting the urinary tract in boys. They occur when abnormal folds of tissue within the urethra obstruct the normal flow of urine from the bladder.
The obstruction may be mild or severe. In some children, PUV is detected during pregnancy because of abnormalities seen on an ultrasound scan. Others are diagnosed after birth when they develop difficulty passing urine, urinary tract infections, or problems involving the kidneys.
Early diagnosis and appropriate treatment are important because prolonged urinary obstruction can affect bladder function and kidney development.
What Are Posterior Urethral Valves?
The urethra is the tube that carries urine from the bladder to the outside of the body.
In boys with PUV, abnormal tissue folds develop within the posterior urethra, the portion of the urethra located just below the bladder.
These folds create resistance to urine flow, making it more difficult for the bladder to empty normally.
As the bladder works against this obstruction, pressure within the urinary tract may increase. Over time, this can affect the bladder, ureters and kidneys.
PUV occurs only in boys and is one of the most important causes of congenital lower urinary tract obstruction.
The severity varies considerably. Some boys have significant urinary obstruction before birth, while others have milder symptoms that become apparent later in childhood.
How Can PUV Affect the Bladder and Kidneys?
The urinary system normally allows urine to flow from the kidneys through the ureters into the bladder, where it is stored until urination.
PUV interferes with this process by obstructing urine flow at the level of the urethra.
Changes in the bladder
The bladder must generate greater pressure to push urine through the narrowed outlet.
Over time, the bladder wall may become thickened, and its ability to store and empty urine normally may be affected.
Some children develop poor bladder compliance, meaning the bladder cannot expand easily at low pressure. Others may have difficulty emptying the bladder completely.
Swelling of the kidneys and ureters
Increased pressure within the urinary tract may be associated with:
Hydronephrosis — swelling of the kidneys due to urine accumulation
Hydroureter — enlargement of the ureters
Vesicoureteral reflux — urine flowing backwards from the bladder towards the kidneys
These changes may affect one or both kidneys.
Effects on kidney function
Severe obstruction during fetal development can interfere with normal kidney formation.
Some boys with PUV are born with kidneys that have already sustained developmental damage. Others may develop worsening kidney function during childhood.
Although surgery can relieve the obstruction, it cannot always reverse kidney damage that occurred before treatment.
This is why ongoing monitoring of kidney function remains an important part of PUV care.
What Are the Symptoms of Posterior Urethral Valves?
The symptoms depend on the child’s age and the severity of the obstruction.
Before birth
PUV may be suspected during routine antenatal ultrasound when the scan shows:
An enlarged or thick-walled fetal bladder
Swelling of one or both kidneys
Dilated ureters
A dilated posterior urethra, sometimes producing a characteristic keyhole appearance
Reduced amniotic fluid in severe cases
These ultrasound findings may suggest urinary tract obstruction, but they do not confirm PUV on their own.
In newborns and infants
Possible signs include:
A weak urinary stream
Difficulty passing urine
A persistently distended bladder
Urinary tract infection
Poor feeding or inadequate weight gain
Reduced urine output in severe cases
Some infants may become unwell because of urinary infection, dehydration or impaired kidney function.
In older children
Boys with less severe obstruction may present later with:
Weak or interrupted urinary stream
Straining to pass urine
Difficulty emptying the bladder
Recurrent urinary tract infections
Daytime urinary incontinence
Bedwetting
Poor growth or abnormalities in kidney function
These symptoms are not specific to PUV and may occur with other urinary conditions.
How Are Posterior Urethral Valves Diagnosed?
Diagnosis usually involves imaging studies, assessment of kidney function and examination of the urethra when indicated.
1. Ultrasound of the kidneys and bladder
Ultrasound is commonly the first investigation.
It can identify hydronephrosis, dilated ureters, bladder wall thickening and other abnormalities that suggest urinary obstruction.
It also helps assess the appearance of the kidneys.
2. Voiding cystourethrogram (VCUG)
A voiding cystourethrogram, also called a micturating cystourethrogram (MCUG), is an important investigation when PUV is suspected.
A small catheter is inserted into the bladder, and contrast material is introduced. X-ray images are taken while the bladder fills and during urination.
The examination may show:
Dilatation of the posterior urethra
Narrowing at the level of the valves
Bladder wall abnormalities
Vesicoureteral reflux
Incomplete bladder emptying
VCUG provides information about the anatomy and function of the lower urinary tract.
3. Blood and urine tests
Blood tests are used to assess kidney function and electrolyte levels.
Urine testing may be required to detect urinary tract infection.
These investigations are particularly important in newborns and children with significant urinary obstruction.
4. Cystoscopy
Cystoscopy involves passing a small camera through the urethra to examine the urinary passage and bladder.
It allows the urologist to directly identify the obstructing valves.
When appropriate, treatment may be performed during the same procedure.
How Are Posterior Urethral Valves Treated?
The main objective of treatment is to relieve urinary obstruction, protect kidney function and support healthy bladder function.
The treatment approach depends on the child’s age, clinical condition, urinary tract anatomy and kidney function.
Initial bladder drainage
In newborns with significant urinary obstruction, a small urinary catheter is usually inserted to drain the bladder.
This helps relieve obstruction while the medical team assesses kidney function, fluid balance and electrolyte levels.
Any urinary infection or associated medical problem is treated before definitive surgery when necessary.
Endoscopic valve ablation
Endoscopic valve ablation is the usual definitive treatment for PUV when the child’s size and condition allow it.
The procedure is performed under general anaesthesia.
A small endoscope is passed through the urethra, allowing the surgeon to visualise the abnormal valve tissue.
The obstructing tissue is then divided using an appropriate endoscopic instrument.
The aim is to establish a more open passage for urine to flow from the bladder.
No external surgical incision is usually required.
Following treatment, a urinary catheter may be left temporarily to allow bladder drainage.
What if the baby is too small for valve ablation?
In some premature or very small infants, the urethra may not safely accommodate the instruments needed for valve ablation.
Temporary urinary diversion, such as a vesicostomy, may be considered when adequate drainage cannot otherwise be achieved.
A vesicostomy creates a small opening from the bladder to the lower abdominal wall, allowing urine to drain.
Definitive valve treatment may be performed later when the child is sufficiently developed and clinically stable.
Not every child requires urinary diversion.
What Happens After PUV Surgery?
Following valve ablation, the medical team monitors the child’s urine output, kidney function and recovery.
Ultrasound examinations may be performed to assess whether swelling of the urinary tract has improved.
In selected cases, repeat VCUG or cystoscopy may be necessary to assess for residual obstruction.
Some boys experience a significant improvement in urine flow and urinary tract dilatation after treatment.
However, bladder abnormalities or kidney impairment may persist even when the obstruction has been successfully relieved.
The response to treatment varies between children.
Why Is Long-Term Follow-Up Necessary?
PUV is not always completely resolved by surgery alone.
Although valve ablation removes the anatomical obstruction, the bladder and kidneys may have been affected during fetal development or before diagnosis.
Some boys develop bladder dysfunction as they grow older.
This may include:
Difficulty storing urine at low pressure
Urinary urgency or incontinence
Incomplete bladder emptying
Recurrent urinary tract infections
Persistent vesicoureteral reflux
Kidney function may also deteriorate over time in some children, particularly those with significant congenital kidney damage.
Monitoring bladder function
Follow-up may involve assessment of urinary symptoms, ultrasound, bladder emptying and, when indicated, urodynamic studies.
Some children require medication or other bladder management strategies to maintain safe bladder pressures and adequate emptying.
Monitoring kidney function
Blood pressure, kidney function, urine protein and kidney growth may be monitored throughout childhood.
Children with impaired kidney function may also require care from a paediatric nephrologist.
Long-term follow-up is often recommended through adolescence and into adult life, depending on the severity of the condition.
Can a Child Have Normal Urination and Kidney Function After PUV Treatment?
Many boys experience improved urinary drainage after valve ablation and can achieve satisfactory bladder function.
However, outcomes depend on several factors, including the severity of obstruction, kidney development before birth and the presence of ongoing bladder dysfunction.
Some children maintain good kidney function, while others develop chronic kidney disease despite appropriate treatment.
Early treatment helps relieve obstruction and may reduce further urinary tract damage, but it cannot reverse all pre-existing kidney abnormalities.
Regular follow-up allows developing problems to be identified and managed.
Frequently Asked Questions
Is posterior urethral valve a birth defect?
Yes. PUV is a congenital condition, meaning it develops before birth. It results from abnormal tissue folds within the posterior urethra that obstruct urine flow.
It is not caused by anything the parents did during pregnancy.
Can posterior urethral valves be detected during pregnancy?
Yes. Antenatal ultrasound may identify an enlarged bladder, dilated kidneys or ureters, and reduced amniotic fluid.
However, these findings can occur in other conditions. Further assessment is needed to establish the diagnosis.
Do all babies with PUV need surgery?
Confirmed PUV generally requires treatment to relieve the obstruction, most commonly by endoscopic valve ablation.
The timing and approach depend on the baby’s clinical condition and the severity of obstruction.
Can PUV come back after surgery?
The valve tissue does not usually grow back after adequate ablation. However, residual valve tissue may occasionally remain and require further treatment.
Persistent urinary symptoms can also result from bladder dysfunction rather than recurrent obstruction.
Can PUV cause kidney failure?
Yes. Severe PUV can cause permanent kidney damage, and some affected boys develop chronic kidney disease or kidney failure.
The risk varies considerably. Kidney function at diagnosis and the degree of underlying kidney damage are important factors in long-term outcomes.
Will my child need another operation?
Others may need repeat endoscopic treatment for residual obstruction or additional procedures for associated urinary tract problems.
Can a boy with PUV lead a normal life?
Many boys attend school, participate in normal activities and grow up with good quality of life.
Some require ongoing treatment for bladder dysfunction or kidney disease.
Long-term outcomes depend on the extent of urinary tract and kidney involvement.
Paediatric Urology Assessment in Kuala Lumpur
Posterior urethral valves require careful assessment of both the urinary obstruction and its effects on the bladder and kidneys.
Dr Roger Anthony Idi is a Consultant Urologist at Prince Court Medical Centre, Kuala Lumpur, with fellowship training in paediatric urology at Great Ormond Street Hospital, London.
Assessment may include reviewing antenatal findings, urinary symptoms, imaging results, kidney function and previous treatment.
Where necessary, care may involve collaboration with paediatricians and paediatric nephrologists, particularly for children with impaired kidney function.
Related Reading
Urinary Stones in Children — another important cause of urinary symptoms in children.
Bedwetting in Children — relevant to urinary control problems, although most bedwetting is unrelated to PUV.
Urodynamic Studies — explaining how bladder storage and emptying function can be assessed.
Paediatric Urology Services — for an overview of Dr Roger’s paediatric practice.