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[Conditions](https://durgical.com/en/conditions/) · [Pediatrics and neonatology](https://durgical.com/en/conditions/)

# Posterior urethral valves

Posterior urethral valves are folds of tissue in a baby boy's urethra that block urine flow and can damage the bladder and kidneys.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Prostatic urethra](https://durgical.com/en/anatomy/prostatic-urethra-seminal-colliculus/)
- [Urinary bladder](https://durgical.com/en/anatomy/urinary-bladder/)
- [Membranous urethra](https://durgical.com/en/anatomy/intermediate-part-of-male-urethra/)
- [Ureters](https://durgical.com/en/anatomy/ureter/)
- [Kidneys](https://durgical.com/en/anatomy/kidney/)
- [External urethral sphincter](https://durgical.com/en/anatomy/female-external-urethral-sphincter/)

## Why it happens

- [Hypertrophy: physiologic and pathologic](https://durgical.com/en/general-pathology/hypertrophy-physiologic-and-pathologic/)
- [Micturition and the bladder reflex](https://durgical.com/en/physiology/micturition-and-the-bladder-reflex/)
- [Ureter, bladder and urethra: urothelium](https://durgical.com/en/histology/ureter-bladder-and-urethra-urothelium/)

## What it is

A congenital obstruction of the male posterior (prostatic) urethra caused by abnormal membranous folds. It is the most common cause of lower urinary tract obstruction in boys and a leading congenital cause of chronic kidney disease in children.

## Who gets it

Occurs only in males, in roughly 1 in 5,000 to 8,000 live-born boys. Most cases are now suspected on prenatal ultrasound; in settings with limited prenatal screening, as in parts of Latin America, diagnosis may come later, after urinary infection, poor growth or kidney failure.

## Causes

- Abnormal development of the posterior urethra early in fetal life, probably from faulty insertion of the Wolffian (mesonephric) duct remnants
- Usually sporadic; a familial pattern is rare

## Risk factors

- Male sex (the only group affected)
- Prenatal finding of bilateral hydronephrosis with a thick-walled, distended bladder

## Pathophysiology

The valves act as a partial dam below the bladder neck. The bladder must generate high pressure to empty, so its wall thickens and becomes trabeculated and poorly compliant. High pressure is transmitted up the [ureters](https://durgical.com/en/anatomy/ureter/), causing hydroureteronephrosis, often vesicoureteral reflux, and damage to the developing kidneys (renal dysplasia). Because fetal urine makes most of the amniotic fluid after mid-pregnancy, severe obstruction causes oligohydramnios, which compresses the fetus and impairs lung growth (pulmonary hypoplasia, Potter sequence).

## Classification

- Young type I: folds extending distally from the verumontanum (most common)
- Young type III: a membrane with a central opening (ring or [diaphragm](https://durgical.com/en/anatomy/diaphragm/)) below the verumontanum
- Young type II (folds toward the bladder neck) is no longer considered obstructive

## Symptoms and signs

- Prenatal: bilateral hydronephrosis, distended thick-walled bladder with dilated posterior urethra (keyhole sign), oligohydramnios
- Newborn: palpable bladder, weak or dribbling urine stream, straining to void
- Respiratory distress from pulmonary hypoplasia in severe cases
- Older infants: urinary tract infection, sepsis, poor feeding and failure to thrive
- Older boys: daytime incontinence, frequency or urgency, poor stream

## Red flags

- No urine output or a weak dribbling stream in a newborn boy
- Respiratory distress at birth with a history of oligohydramnios
- Fever and lethargy suggesting urosepsis
- Rising creatinine, hyperkalemia or acidosis
- Vomiting and dehydration with poor weight gain

## Diagnosis

**Clinical**
Suspected in a boy with prenatal bilateral hydronephrosis and a full bladder, or in a newborn or infant boy with a poor stream, urinary infection or [kidney](https://durgical.com/en/anatomy/kidney/) dysfunction.

**Tests**
Serum creatinine (trend after the first days of life, since newborn values reflect the mother's), electrolytes and acid-base status, urinalysis and urine culture. Cystoscopy both confirms and treats. Urodynamic studies assess bladder function at follow-up.

**Imaging**
Voiding cystourethrogram (VCUG) is the key test: dilated, elongated posterior urethra with an abrupt narrowing at the valve, a trabeculated bladder and often reflux. Renal and bladder ultrasound shows hydronephrosis, a thick-walled bladder and signs of dysplasia.

## Differential diagnosis

- Prune belly syndrome
- Bilateral ureteropelvic or ureterovesical junction obstruction
- High-grade vesicoureteral reflux without obstruction
- Neurogenic bladder (for example with spina bifida)
- Urethral atresia or stricture

## Goal of treatment

Relieve the obstruction early, protect kidney function and manage the bladder for life to delay or prevent kidney failure.

## Treatment

**Acute**
At birth: bladder drainage with a urethral catheter, correction of fluid, electrolyte and acid-base problems, and respiratory support if needed.

**Surgical**
Endoscopic valve ablation (cystoscopic incision of the valves) once the baby is stable; a temporary vesicostomy if the urethra is too small.

**Medical**
Antibiotic treatment of urinary infections and, in selected children, prophylaxis; anticholinergic drugs for an overactive bladder; management of chronic kidney disease.

**Follow-up**
Lifelong follow-up of kidney function, blood pressure, growth and bladder function (valve bladder), with clean intermittent catheterization when the bladder empties poorly.

## Complications

- Chronic kidney disease and kidney failure needing dialysis or transplant
- Pulmonary hypoplasia and neonatal death in severe cases
- Recurrent urinary tract infection and urosepsis
- Valve bladder syndrome: poorly compliant, poorly emptying bladder with incontinence
- Polyuria from tubular damage, with risk of dehydration

## Prognosis

Depends on the degree of kidney damage before relief. A low creatinine nadir in the first year of life predicts better long-term kidney function; a substantial minority (up to about a quarter or more) reach kidney failure over their lifetime.

## Prevention

- No known prevention; prenatal ultrasound allows planned delivery and early drainage and ablation

## Test yourself

Think of the answer, then tap the question to see it.

## What is the most common cause of congenital lower urinary tract obstruction in boys?

Posterior urethral valves.

## Which study is the key test to diagnose posterior urethral valves?

Voiding cystourethrogram, showing a dilated, elongated posterior urethra with abrupt narrowing at the valves.

## Why can posterior urethral valves cause respiratory distress at birth?

Severe obstruction reduces fetal urine and amniotic fluid; oligohydramnios causes pulmonary hypoplasia (Potter sequence).

## What is the definitive first-line treatment once the newborn is stable?

Endoscopic (cystoscopic) valve ablation, after initial bladder drainage with a catheter.

## Which laboratory marker in the first year predicts long-term kidney outcome?

The lowest (nadir) serum creatinine after relief of obstruction.

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## Related conditions

- [Hydronephrosis and obstructive uropathy](https://durgical.com/en/conditions/hydronephrosis-and-obstructive-uropathy/)
- [Vesicoureteral reflux](https://durgical.com/en/conditions/vesicoureteral-reflux/)
- [Chronic kidney disease](https://durgical.com/en/conditions/chronic-kidney-disease/)
- [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/)
- [Congenital kidney anomalies (horseshoe kidney, renal agenesis)](https://durgical.com/en/conditions/congenital-kidney-anomalies/)
- [Neurogenic bladder](https://durgical.com/en/conditions/neurogenic-bladder/)
- [Acute kidney injury](https://durgical.com/en/conditions/acute-kidney-injury/)
- [Hyperkalaemia](https://durgical.com/en/conditions/hyperkalaemia/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Posterior Urethral Valves](https://www.childrenshospital.org/conditions/posterior-urethral-valves) (Boston Children's Hospital, 2024); [Potter syndrome](https://medlineplus.gov/ency/article/001268.htm) (MedlinePlus (U.S. National Library of Medicine), 2024).

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Source: https://durgical.com/en/conditions/posterior-urethral-valves/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/posterior-urethral-valves/