eMedicine Specialties > Pediatrics: Surgery > Urology

Posterior Urethral Valves

Author: Martin David Bomalaski, MD, FAAP, Pediatric Urologist, Alaska Southcentral Urology Specialists
Contributor Information and Disclosures

Updated: Jun 12, 2008

Introduction

Background

The first description of posterior urethral valves (PUVs) was made by Hugh Hampton Young. PUVs represent a spectrum of severity, ranging from disease incompatible with postnatal life to disease that is minimal and may not manifest until later in life. Treatment of PUVs remains a clinical challenge, requiring active management from infancy into adulthood to avoid progressive dysfunction and deterioration of both the upper and lower urinary tracts.

Pathophysiology

During embryogenesis, the most caudal end of the Wolffian duct is absorbed into the primitive cloaca at the site of the future verumontanum in the posterior urethra. In healthy males, the remnants of this process are the posterior urethral folds, called plicae colliculi. Histological studies suggest that PUVs are formed at approximately 4 weeks' gestation, as the Wolffian duct fuses with the developing cloaca.

Young popularized a classification of PUVs.¹ Abnormally high insertion and fusion of these primitive folds were believed to be the origins of 95% of PUVs; this type was referred to as type I PUVs. Although Young described type II PUVs, most pediatric urologists believe that these are not obstructing valves but simply hypertrophy of the plicae colliculi. Also described by Young, type III PUVs constitute a septum at the junction of the posterior and anterior urethra, instead of a sail-like valve. Type III PUVs are believed to originate from incomplete dissolution of the urogenital membrane. This classification has no clinical value and is now considered outdated.

Congenital obstructing posterior urethral membrane (COPUM) was first proposed by Dewan and Goh and was later supported by histological studies by Baskin.² This concept proposes that, instead of a true valve, a persistent oblique membrane is ruptured by initial catheter placement and, secondary to rupture, forms a valvelike configuration.

PUV represents a spectrum of severity. The degree of obstruction caused by this abnormality widely varies depending on the configuration of the obstructive membrane within the urethra. The morbidity of PUVs is not merely limited to transient urethral obstruction; however, the congenital obstruction of the urinary tract at a critical time in organogenesis may have a profound and lifelong effect on kidney, ureteral, and bladder function.

Renal insufficiency is caused by PUVs in approximately 10-15% of children undergoing renal transplant, and approximately one third of patients born with PUVs progress to end-stage renal disease (ESRD).

Moreover, children with PUVs develop thickened bladders because of increased collagen deposition and muscle hypertrophy within the bladder wall. Hypertrophy and hyperplasia of the detrusor muscle and increases in connective tissue decrease bladder compliance during filling. Bladder emptying occurs with high intravesical pressures, which can be transmitted to the ureters and kidneys. These patients are susceptible to incontinence, infection, and progressive renal damage.

Frequency

United States

PUV is the most common cause of lower urinary tract obstruction in male neonates; the reported incidence is 1 per 8,000 to 1 per 25,000 live births.

Mortality/Morbidity

PUVs are the cause of renal insufficiency in approximately 10-15% of children undergoing renal transplant, and approximately one third of patients born with PUV progress to ESRD.

Sex

PUVs exclusively occur in males. The homolog to the male verumontanum from which the valves originate is the female hymen.

Age

Diagnosis is usually made before birth or at birth when a boy is evaluated for antenatal hydronephrosis. Before the era of prenatal ultrasonography, PUVs were discovered during evaluation of urinary tract infection (UTI), voiding dysfunction, or renal failure. Although rare, adult presentation of PUVs has been described in case reports, with symptoms varying from obstructive voiding symptoms to postejaculatory dysuria. In the presonography era, late presentation of PUV was considered a good prognostic sign suggestive of a lesser degree of obstruction.

Clinical

History

• Prenatal diagnosis
  • The widespread use of antenatal ultrasonography and the sophisticated neonatal care available in most developed countries has enabled diagnosis of posterior urethral valves (PUVs) in many individuals in the prenatal timeframe.
  • Diagnosis is usually made before or at birth when a boy is evaluated for antenatal hydronephrosis.
  • In 1989, Thomas reported that 10% of patients with prenatal hydronephrosis detected by ultrasonography had PUVs.³
  • Despite widespread use of antenatal ultrasonography, some patients with PUVs present later in life.
  • In a 1993 report, Dinneen et al reported the sensitivity of antenatal ultrasonography to be only 45% in detecting PUVs in 45 patients who presented when younger than 6 months.⁴ With improvements in technology, the sensitivity has increased over the last 10 years.
  • Those patients with PUVs not diagnosed on prenatal ultrasonography and who do not manifest overt urinary pathology are at risk of delayed presentation of PUVs.
• Delayed presentation
  • UTI, diurnal enuresis in boys older than 5 years, secondary diurnal enuresis, voiding pain or dysfunction, and decreased force of stream may indicate the presence of PUVs.⁵
  • PUVs are sometimes discovered during evaluation of abdominal mass or renal failure.
• Incidental diagnosis: Hydronephrosis or proteinuria found on examination for unrelated conditions may be the first sign of PUVs.

Physical

Most patients have normal findings upon physical examination. When present, abnormal physical findings are the result of severe renal insufficiency.

• Neonates may present with severe pulmonary distress due to underdevelopment of the lung caused by oligohydramnios. An appropriate volume of amniotic fluid (produced by the kidneys) is necessary for complete and proper branching of the bronchial tree and alveoli. Physical findings can include the following:
  • Poor fetal breathing movements
  • Small chest cavity
  • Abdominal mass (ascites)
  • Potter facies
  • Limb deformities (skin dimpling)
  • Indentation of the knees and elbows due to compression within the uterus
• In older children, physical findings can include poor growth, hypertension, and lethargy. An intermittent or weak urinary stream is a nonreliable sign.

Causes

A PUV is a congenital obstruction caused by a malformation of the posterior urethra. The significance of this obstruction depends on the secondary effects on the bladder, ureters, and kidneys.

• Type I PUV: This type of obstruction is believed to be secondary to abnormal insertion and absorption of the most distal aspects of the Wolffian ducts during bladder development. In the healthy male, the remnants of these ducts are observed as the plicae colliculi.
• Type III PUV: These valves are observed as a membrane in the posterior urethra believed to originate from incomplete canalization between the anterior and posterior urethra.

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