Posterior Urethral Valves 

Updated: Apr 02, 2020
Author: Martin David Bomalaski, MD, FAAP; Chief Editor: Marc Cendron, MD 

Overview

Practice Essentials

Posterior urethral valves (PUVs), first described by Hugh Hampton Young et al in 1919,[1]  cause bladder obstruction in males that can manifest along a spectrum of severity, ranging from disease incompatible with postnatal life to conditions that have such minimal impact that they may not manifest until later in life.

Treatment of PUVs remains a clinical challenge, requiring long-term management from early infancy into adulthood in order to avoid progressive bladder dysfunction and deterioration of both upper and lower urinary tracts.[2]  (See Treatment.)

Medical management relates to treatment of the secondary effects of the valves. Short-term goals involve treatment of pulmonary distress, immediate relief of urethral obstruction, and fluid and electrolyte management. In children who survive the pulmonary distress, the long-term issues include treatment of bladder dysfunction and renal insufficiency.

Surgical care of the patient with PUV varies according to age, bladder status, and renal status. Procedures that may be considered include postnatal primary valve ablation, vesicostomy, cutaneous ureterostomy, augmentation cystoplasty, and continent appendicovesicostomy.

Fetal intervention for PUV[3]  is discussed further elsewhere (see Fetal Surgery for Urinary Tract Obstruction).

Pathophysiology

During the early stages of 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. Histologic studies suggest that PUVs are formed at approximately 4 weeks' gestation, as the wolffian duct fuses with the developing cloaca.

Congenital obstructing posterior urethral membrane (COPUM) was first proposed by Dewan and Goh and was later supported by histologic studies by Baskin.[4] 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.

The morbidity of PUVs is not merely limited to transient urethral obstruction. The congenital obstruction of the urinary tract at a critical time in organogenesis may profoundly affect lifelong kidney, ureteral, and bladder function. In a dynamic process, bladder dysfunction may cause ongoing and progressive renal deterioration. Renal insufficiency is caused by PUVs in approximately 10-15% of children undergoing renal transplantation, and approximately one third of patients born with PUVs progress to end-stage renal disease (ESRD).

Moreover, as a result of the obstructive process, increased collagen deposition and muscle hypertrophy can significantly thicken the bladder wall. Hypertrophy and hyperplasia of the detrusor muscle and increases in connective tissue limit bladder compliance during filling. Bladder emptying then occurs at high intravesical pressures, which, in turn, can be transmitted to the ureters and up into the renal collecting system. Ultimately, patients with PUV may be susceptible to incontinence, infection, and progressive renal damage.

As patients with PUV age, bladder decompensation may develop, resulting in detrusor failure and increased bladder capacity. Many boys with PUV will develop larger-than-expected bladder volumes by age 11 years, possibly as a consequence of overproduction of urine caused by tubular dysfunction and an inability to concentrate urine (nephrogenic diabetes insipidus).

Bladder function may change at puberty, resulting in high-pressure, chronic retention and necessitating the need for lifelong bladder management.[5] Symptoms of bladder dysfunction may persist into adulthood in as many as one third of patients and include urinary incontinence in as many as 15% of adults with a history of PUV.[6]

Young's original description divided PUVs into three types, as follows[1] :

  • Type I - Valves representing folds extending inferiorly from the verumontanum to the membranous urethra (~95% of PUVs)
  • Type II - Bicuspid valves as leaflets radiating from the verumontanum proximally to the bladder neck
  • Type III - Valves as concentric diaphragms within the prostatic urethra, either above or below the verumontanum (~5% of PUVs)

Most pediatric urologists now regard the existence of type II PUVs as doubtful.

Etiology

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.

 A type I PUV is believed to result from 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 PUVs are observed as a membrane in the posterior urethra believed to originate from incomplete canalization between the anterior and the posterior urethra.

Epidemiology

In the United States, PUV is the most common cause of lower urinary tract obstruction in male neonates; the reported incidence ranges from 1 per 8000 to 1 per 25,000 live births.

In a study of referrals of boys diagnosed with suspected or confirmed PUV in the United Kingdom and Ireland, the calculated annual incidence of PUV was 1 in 3800.[7] Overall, 35% of cases presented antenatally, 42% in infancy, and 23% late. Boys who were diagnosed antenatally had significantly higher postnatal plasma creatinine, more hydroureteronephrosis, and renal dysplasia than those diagnosed in infancy or later.

PUVs are usually diagnosed before birth or at birth when a boy is evaluated for antenatal hydronephrosis. Before the era of antenatal ultrasonography (US), 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 ranging from obstructive voiding symptoms to postejaculatory dysuria. In the pre-US era, a late presentation of PUV was considered a good prognostic indicator suggestive of a lesser degree of obstruction.

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

Prognosis

Over the past 30 years, the prognosis of children with PUV has steadily improved. In the past, most children were found to have PUV only after presenting with urosepsis or progressive renal insufficiency. Older series demonstrated mortality figures approaching 50% by late adolescence. Today, most individuals with PUV are discovered when antenatal US reveals hydronephrosis. Prompt resolution of bladder obstruction, aggressive treatment of bladder dysfunction, and improved surgical techniques have lowered the neonatal mortality to less than 3%.

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 in their lifetimes. Early initial presentation, pneumothorax, bilateral vesicoureteral reflux (VUR), and recurrent UTIs after valve ablation are all associated with risk for progression to ESRD.[8]

As the child grows, renal metabolic demand increases proportionately. Failure of creatinine to nadir below 0.8 mg/dL in the first year of life is an indication of limited renal reserve. These patients are at risk for progression to ESRD with somatic growth, such as occurs at puberty.

Improved dialysis and transplantation techniques have significantly improved not only mortality but also quality of life for these children . Additionally, medical and surgical management can achieve urinary continence in nearly all patients.

An interesting group of patients are those with VUR dysplasia (VURD) syndrome. In these patients, one kidney is hydronephrotic, nonfunctioning, and has high-grade VUR. The high-grade VUR is thought to act as a pop-off valve, leading to reduced overall bladder pressures and preservation of contralateral renal function.

In the past, these patients were thought to have a better outcome as a result of preserved renal function in one kidney at the sacrifice of the other. Subsequent work by Narasimhan et al suggested that although short-term serum creatinine levels may be favorable, these patients may suffer long-term adverse renal function with hypertension, proteinuria, and renal failure.[9] In the long run, VURD syndrome may not have the favorable outcome it was once thought to have.

Patient Education

PUV is a lifelong condition that requires continued medical management. Because of this, both the physician and family must understand the potential long-term complication of renal deterioration if bladder function is not adequately treated.[10]

Patients and families need realistic expectations regarding continence. Although continence is achievable in nearly all patients, it often depends on adherence to a timed voiding schedule and intermittent catheterization.

Patients and families must also realize that medications, such as anticholinergics and suppressive antibiotics, are for controlling the symptoms of PUV and are not curative.

For patient education resources, see the Kidneys and Urinary System Center, as well as Bladder Control Problems.

 

Presentation

History

Antenatal diagnosis

The widespread use of antenatal ultrasonography (US) has enabled diagnosis of posterior urethral valves (PUVs) in many more individuals, with most cases of bladder outlet obstruction recognized in the second and third trimester of gestation. The diagnosis is usually made before or at birth when a boy is evaluated for antenatal hydronephrosis. Despite widespread use of antenatal US, some patients with PUVs do present later in life (see below).

In 1989, Thomas reported that 10% of patients with antenatal hydronephrosis detected by US had PUVs.[11]  In a 1993 report, Dinneen et al reported the sensitivity of antenatal US to be only 45% in detecting PUVs in 45 patients who presented when younger than 6 months.[12] With improvements in technology, the sensitivity has increased over the last 10 years.

Patients who have PUVs that are not diagnosed on antenatal US and who do not present with overt urinary pathology are at risk for delayed presentation of PUVs.

Delayed presentation

Indicators of possible PUVs later in childhood include the following[13] :

PUVs manifest along a spectrum of disease severity. The clinical significance of minivalves has been debated. Some studies have indicated that the significance of minor radiographic narrowing in older boys may be differentiated by means of urodynamic studies. Those with detrusor/sphincter dyssynergy may have functional or nonanatomic obstruction, and those with detrusor/sphincter synergy may have true anatomic obstruction that benefits from surgical incision.[14]

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 Examination

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

Neonates may present with severe pulmonary distress caused by lung underdevelopment lung due to 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)
  • 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 an unreliable sign. A large lower abdominal mass may represent a markedly distended urinary bladder.

 

DDx

Diagnostic Considerations

In addition to the conditions listed in the differential diagnosis, other problems to be considered include the following:

  • Anterior urethral valves
  • Urethral stricture disease
  • Detrusor sphincter dyssynergy
  • Diurnal urinary incontinence
  • Pediatric renal insufficiency

Differential Diagnoses

 

Workup

Laboratory Studies

For the first 24 hours after birth, the infant's serum chemistries are the same as the mother's. Therefore, serum values for creatinine and blood urea nitrogen (BUN) should be obtained at least 24 hours after birth. In utero, the placenta functions as the major blood filter for the fetus, with waste passed on to the mother. Observing serial serum chemistries for several days to weeks is important to determine the true status of the newborn's renal function.

The normal newborn kidney is still undergoing maturation at birth, and the infant's glomerular filtration rate (GFR) continues to improve during the first several months of life. Because of renal immaturity at birth, the newborn is unable to concentrate urine and is susceptible to dehydration. This defect is exacerbated by renal dysplasia such as that found with posterior urethral valves (PUVs).

As renal maturation continues, creatinine clearance normally improves. If significant renal dysplasia or damage has occurred, the serum creatinine fails to reach a normal level during the first year of life. Serum creatinine levels higher than 0.8 mg/dL during the first year of life have been demonstrated to be associated with poor long-term renal function; thus, such levels are considered a negative prognostic indicator.

Imaging Studies

Ultrasonography

Antenatal ultrasonography (US) has been found to be reasonably accurate in distinguishing PUV from vesicoureteral reflux (VUR).[15]

Every child with antenatal hydronephrosis should be assessed with renal and bladder US in the immediate postnatal period,[16] with a focus on the appearance of the renal parenchyma, any evidence of renal collecting system dilatation, the thickness of the bladder wall, and the presence or absence of ascites. The quantity (total area) and quality (corticomedullary differentiation and renal echogenicity) of the renal parenchyma on initial postnatal US have prognostic value for determining the future risk of stage 5 chronic kidney disease.[17]

Because newborns commonly have relative hypovolemia during the first few days of life, it is recommended to perform US after the first week of life if findings from the first US examination were normal in a child with previously diagnosed antenatal hydronephrosis before making a final determination that the hydronephrosis has resolved (see Presentation, History).

Contrast-enhanced serial voiding urosonography has been sugegsted as a useful complementary test in pediatric patients with PUVs.[18]  

Voiding cystourethrography

The key to the workup of any child with antenatal hydronephrosis is voiding cystourethrography (VCUG). VCUG should be performed under fluoroscopy, with imaging of the posterior urethra, especially during the voiding phase. Cycling the bladder during the study several times improves the sensitivity of the evaluation.

The diagnosis of PUV is indicated by visualization of the valve leaflets. Other clues to the diagnosis are a thickened trabeculated bladder, a dilated or elongated posterior urethra, and a hypertrophied bladder neck (see the first image below). Diverticula, cellules, VUR, and reflux into the ejaculatory ducts secondary to elevated bladder and urethral pressures may also be present (see the second image below).

Note hypertrophied bladder neck and dilated poster Note hypertrophied bladder neck and dilated posterior urethra proximal to valve narrowing.
Note irregular trabeculated bladder and high-grade Note irregular trabeculated bladder and high-grade vesicoureteral reflux.

VCUG may miss late-presenting cases of PUV.[19]

Renal scintigraphy

Renal scintigraphy, though not necessary in every child, may be helpful in some cases. It should not be performed in the neonatal period, because renal immaturity does not allow for accurate estimation of renal function. If renal dysplasia is suspected, nuclear imaging can determine relative renal function. In some cases, children with a very thickened bladder wall may have secondary ureterovesical junction obstruction due to bladder hypertrophy.

Tc-dimercaptosuccinic acid (DMSA), glucoheptonate, and mercaptoacetyltriglycine (MAG-3) renal scintigraphy are cortical imaging studies that provide information about relative renal function (each kidney relative to the other) and intrarenal function (eg, photopenic areas within the kidney indicate scarring or dysplasia). Additionally, the MAG-3 renal scan with furosemide provides information about renal drainage and possible obstruction.

Other Tests

Urodynamic evaluation provides information about bladder storage and emptying. In the older child, the mature bladder should store urine at a low pressure and then completely empty at appropriate pressures. A newborn's bladder may not empty completely under normal circumstances.

The term valve bladder is used to describe patients with PUV and a fibrotic noncompliant bladder. These patients are at risk of developing hydroureteronephrosis, progressive renal deterioration, recurrent infections, and urinary incontinence.

Patients with PUV require periodic urodynamic testing throughout childhood because bladder compliance may further deteriorate over time.

Procedures

Cystoscopy

Cystoscopy serves both diagnostic and therapeutic functions in these infants. Appropriately-sized cystoscopes (< 8 French) are needed to avoid injury to the urethra.

Diagnostic

Confirmation with cystoscopy is required in every child in whom PUV is suggested after VCUG. In some, the filling defect observed on VCUG may represent only external sphincter contraction during voiding; in others, the valve leaflets are confirmed.

Therapeutic (ie, transurethral incision of PUVs)

Multiple techniques are described for PUV ablation. Disruption of the obstructing membrane by blind passage of a valve hook is now only of historic interest. Currently, valves are disrupted under direct vision by cystoscopy using an endoscopic loop, Bugbee electrocauterization, or laser fulguration. In extremely small infants (< 2 kg), a 2-French Fogarty catheter may be passed either under fluoroscopic or direct vision for valve disruption.[20] This is performed in the least traumatic fashion possible to avoid secondary urethral stricture or injury to the urethral sphincter mechanism.

Vesicostomy

In some patients, the urethra may be too small for the available cystoscopic instrumentation. Fortunately, because of continued advancements in pediatric endoscopic equipment, this is an uncommon occurrence. When this situation arises, a temporary vesicostomy may be performed.

Outpatient intermittent catheterization via a sensate and dilated posterior urethra and bladder neck may not be feasible in all patients. A minivesicostomy in the subinguinal region can allow continued, intermittent passage of a catheter when the urethra is not available.[21]

 

Treatment

Approach Considerations

Newborn care

In newborns with posterior urethral valves (PUVs), the first step in treatment is to relieve bladder outlet obstruction by placing a urethral catheter. Cystoscopic valve ablation or vesicostomy can then be performed when the child is stable. in rare cases, a urethral catheter cannot be placed, because of hypertrophy of the bladder neck. These patients require cystoscopy under anesthesia for catheter placement, suprapubic tube placement, or primary vesicostomy.

Therefore, care of the newborn depends on having adequate instrumentation (eg, pediatric cystoscopic equipment) and expertise (eg, pediatric radiologist, pediatric urologist, pediatric anesthesiologist). If these services are unavailable, place a catheter (if possible) and transfer the child to an appropriate facility.

Care of the older child

Care of the older child also requires adequate equipment and expertise. Periodic radiologic and urodynamic evaluation is important to monitor the upper urinary tract and bladder changes. These evaluations occur over an extended period of time and rarely constitute an emergency. These patients require a timely referral to a center where appropriate services are available.

Medical Care

Medical management of PUVs relates to treatment of the secondary effects of the valves. Adequate care involves a team approach that includes a neonatologist, a general pediatrician, a pediatric urologist, and a pediatric nephrologist. Short-term goals involve treatment of pulmonary distress, immediate relief of urethral obstruction (placement of a 5-French feeding tube), and fluid and electrolyte management. In children who survive the pulmonary distress, the long-term issues include treatment of bladder dysfunction and renal insufficiency.

Renal insufficiency

Few patients present with bilateral renal dysplasia at birth. In the past, if patients did not die of associated pulmonary insufficiency, they died of progressive renal insufficiency. Advances in peritoneal dialysis have made it possible for some to may be treated successfully from birth. If growth is adequate, renal transplantation is often possible after the first year of life.[22, 23]

Approximately one third of patients with PUVs eventually progress to end-stage renal disease (ESRD) and will require dialysis or transplantation. Progression of ESRD is accelerated at the time of puberty as a consequence of the increased metabolic workload placed on the kidneys. Growth in these children may be significantly below the reference range for the child's age. Adequate caloric intake and protein nutrition are essential to growth but may also accelerate the rise in serum creatinine levels.

Renal dysfunction can be accelerated by recurrent infections and elevated bladder pressures. Treatment of the lower urinary tract may influence the progression of upper urinary tract disease.

Bladder dysfunction

All male children with antenatal hydronephrosis should undergo voiding cystourethrography (VCUG) shortly after birth to exclude PUV. While awaiting the study results, place a 5- or 8-French urethral catheter to allow for bladder drainage. If valves are confirmed, they can be incised within the first few days of life. However, the newborn urethra may be too small to accommodate available equipment. In these individuals, a vesicostomy can be performed as a temporary solution until urethral growth has been adequate to allow transurethral incision.

Secondary ureterovesical junction obstruction from bladder hypertrophy is a controversial issue. Supravesical urinary diversion procedures (eg, cutaneous ureterostomies) are reserved for patients who appear to have ureterovesical junction obstruction. This is very uncommon.

Later in childhood, severe or prolonged urethral obstruction can lead to a fibrotic, poorly compliant bladder. This occurs when the developing bladder is exposed to high pressures from bladder outlet obstruction, leading to increases in bladder collagen deposition and detrusor muscle hypertrophy and hyperplasia. These bladders manifest poor compliance, leading to elevated storage pressures. This, in turn, leads to increased risk of reflux, hydroureteronephrosis, and urinary incontinence.

Use of urodynamic testing to assess bladder compliance helps identify patients at risk. Some patients may respond to anticholinergic medication, such as oxybutynin.[24, 25] Institution of clean intermittent catheterization (CIC) may aid some patients in achieving continence by preventing the bladder from overfilling. In patients who do not gain adequate bladder capacity and safe compliance despite optimal medical management, augmentation cystoplasty may be required.

Surgical Care

Surgical care of the patient with PUV varies according to age, bladder status, and renal status. Antenatal surgery has been reported in patients diagnosed with PUV with the goal of improving postnatal outcomes. Antenatal hydronephrosis is detectable only after renal development has occurred and urine production has started.

Improvements in antenatal ultrasonography (US) raised hopes that earlier intervention with vesicoamniotic shunting (VAS) would improve postnatal renal function.[26] However, identification of those patients who may benefit from early intervention remained elusive. To date, improvement in renal function has been difficult to demonstrate. A systematic review and meta-analysis by Nassr et al found that VAS appeared to confer an advantage in terms of perinatal survival but was not clearly beneficial in terms of 1- to 2-year survival and postprocedural renal function.[27]  The precise role of antenatal intervention remains to be established.

Urinary drainage

Postnatal primary valve ablation

Ideal treatment involves transurethral incision of the PUV during the first few days of life. Current infant resectoscopes are available in 8 French and smaller sizes. The valves can be incised at the 12-, 5-, and 7-o'clock positions, with either a cold knife or an electrocautery. Some surgeons prefer to leave a catheter in place for 2-3 days after the procedure. The timing of the postoperative VCUG varies and ranges from several days to several months.

Comparison of the posterior urethral diameter with the anterior urethral diameter can provide an objective measure of valve ablation. In most patients, the posterior urethra is markedly dilated. Postincision diameter should decrease if the incision is successful. The normal posterior-to-anterior urethral ratio is approximately 2.3. Approximately two thirds of patients have successful valve ablation with one procedure, manifested by a postincision ratio of 3.1 or less.[28] One third of patients require a second incision to achieve this level of posterior urethral reduction.

Because approximately one third of patients will require a second valve incision, some authors recommend routine surveillance cystoscopy 1-2 months after the initial incision to evaluate and treat any residual valvular obstruction.[29]

In a study by Shirazi et al, factors significantly associated with a higher incidence of obstructive remnant leaflets after valve ablation for PUV included the following[30] :

  • Younger age at the time of surgery
  • Hyperechogenicity of renal parenchyma
  • Presence of vesicoureteral reflux (VUR)
  • Grade 4 or 5 reflux preoperatively

Vesicostomy

When urethral size precludes safe valve ablation, a communicating channel between the bladder and lower abdominal wall (ie, vesicostomy) can be created to provide bladder drainage.

Generally, an 18- to 20-French stoma is created approximately midway between the pubis and the umbilicus in the midline. Take care to bring the dome of the bladder to the skin and to limit the stomal size to prevent prolapse of bladder urothelium through the vesicostomy. Formation of too small a stoma results in stomal stenosis and inadequate bladder emptying; formation of too large a stoma allows for bladder prolapse. Vesicostomy use has decreased because most patients can be safely drained and can undergo valve ablation.

Cutaneous ureterostomies

Bilateral cutaneous ureterostomies can also be placed to provide for urinary drainage. Techniques for cutaneous ureterostomy include the following:

  • End stomal ureterostomy
  • Loop ureterostomy
  • Y-ureterostomy (in which the ureter is divided and one end is brought to the skin and the other is reanastomosed in a ureteroureterostomy)
  • Ring ureterostomy

Potential complications of cutaneous ureterostomies, all of which are rare, include the following:

  • Ureteral devascularization
  • Inadequate drainage
  • Stomal stenosis

Secondary bladder surgery

Augmentation cystoplasty

Indications for bladder augmentation include inadequately low bladder storage volumes and high bladder pressures despite anticholinergic medication and CIC. The ileum is most commonly used; however, the large bowel, stomach, and ureter are also used, depending on clinical conditions and surgeon preference.

Before an augmentation procedure is undertaken, the implications of bladder augmentation should be carefully reviewed with parent and family. Augmentation should only be offered to patients willing to commit to lifelong intermittent catheterization.

Potential complications include the following:

  • Bladder rupture (~10% of patients)
  • Electrolyte disturbances, which may be worsened by the placement of intestinal mucosa in contact with urine, especially in those with a serum creatinine greater than 2 mg/dL
  • Mucus production, which can be a source of catheter blockage and may be a nidus for stone formation

The future risk of neoplasia has not yet been defined in these patients, but several cases of malignant degeneration in augmented bladders have been reported. Augmentation cytoplasty does not appear to have an adverse effect on overall renal outcome in PUV patients who undergo kidney transplantation, though it is associated with a higher incidence of recurrent urinary tract infection (UTI).[31]

Despite these risks, augmentation can significantly improve patient lifestyle in those who have intractable incontinence as a consequence of poor compliance and bladder overactivity. By lowering intravesical pressures, the upper urinary tract may also be protected.

Continent appendicovesicostomy

Also called the Mitrofanoff technique, continent appendicovesicostomy involves placing a nonrefluxing tubular conduit for catheterization between the bladder and skin to provide an alternative channel for catheterization. In children with PUVs, institution of intermittent catheterization through a sensate urethra can be difficult. In addition, some patients may have a highly dilated proximal urethra that may not be easily catheterized. The stoma often can be hidden in the umbilicus to provide acceptable cosmesis. The appendix, ureter, and tubularized bowel can be used for formation of this channel.

Complications

Pulmonary hypoplasia secondary to intrauterine renal dysfunction and oligohydramnios is the primary cause of patient death.[32] Other complications of PUV are generally secondary to chronic bladder changes, leading to elevated detrusor pressures. This, in turn, leads to progressive renal damage, infection, and incontinence.

Renal insufficiency

Historically, of patients with adequate pulmonary function, approximately 25% died of renal insufficiency in the first year of life, 25% died later in childhood, and 50% survived to adulthood with varying degrees of renal function. Today, with the advent of better techniques in the treatment of pediatric renal insufficiency, most of these children can be expected to survive.

The goal of treatment is to preserve the maximal obtainable renal function for each patient. This entails aggressive treatment of infections and bladder dysfunction.

Certain risk factors for progression of PUV have been identified. Elevated nadir creatinine, defined as greater than 1 mg/dL, measured during the first year of life has been identified as a risk factor for development of future renal insufficiency. Additionally, bladder dysfunction with poor compliance, elevated leak point pressures, and the need for CIC have been identified as predictive of eventual renal deterioration.[32]

Vesicoureteral reflux

VUR (see the image below) is commonly associated with PUVs and is present in as many as one third of patients. In most children, VUR is believed to be due to an abnormal insertion of the ureter into the bladder. When associated with PUV, reflux is generally secondary to elevated intravesical pressures. Therefore, the treatment of VUR in patients with PUVs involves treatment of intravesical pressures using anticholinergics, timed voiding, double voiding, intermittent catheterization, and, at times, bladder augmentation.

Note irregular trabeculated bladder and high-grade Note irregular trabeculated bladder and high-grade vesicoureteral reflux.

Urinary tract infections

Recurrent UTIs are common in patients with PUVs. Elevated intravesical pressures predispose patients to infection, possibly by altering urothelial blood flow. Additionally, patients with PUV may have elevated postvoid residual urine volumes, leading to stasis of urine. Dilated upper urinary tracts, with or without VUR, further elevate UTI risk.

UTI management is directed at lowering bladder pressures (anticholinergic medication), lowering postvoid residual urine volume (via CIC), and, at times, administering prophylactic antibiotics.

Urinary incontinence

The same factors that lead to VUR and UTI also lead to urinary incontinence. Correct management of bladder function depends on adequate bladder evaluation with urodynamic studies. Lowering bladder pressure, improving bladder compliance, and minimizing postvoid residual urine volume contribute to attainment of urinary continence. In some, bladder augmentation may be needed.

Diet

Dietary restrictions depend on renal status. Avoiding the progression of renal deterioration while supporting growth requires careful regulation of protein intake, which is best managed under the care of a pediatric nephrologist.

In the absence of renal insufficiency, no modification of diet is needed.

Activity

Unless complications such as renal insufficiency occur, activity can generally remain unrestricted. Urinary incontinence may present a social barrier. This can often be managed with anticholinergic therapy with or without CIC.

Prevention

Because PUV is a congenital anomaly of unknown origin, it is not preventable. Urinary organogenesis occurs around week 8 of gestation, long before imaging can accurately assess anatomy. Urinary tract dilation is generally not detectable until approximately week 18 of gestation.

Subsequent renal deterioration and bladder changes can be treated and minimized with adequate follow-up care.

Consultations

The child with PUV is best cared for by employing a team approach.

Pediatrician and neonatologist

The most life-threatening problem in the newborn period is the potential pulmonary hypoplasia related to renal dysfunction in utero. This may be associated with oligohydramnios. At birth, pneumothoraces may be present, thus complicating pulmonary management. Upon birth, new metabolic demands are made on the infant kidneys. Urinary stasis and elevated detrusor pressures are risk factors for urosepsis in the newborn.

Generally, treatment is coordinated best by establishing a primary pediatrician or pediatric service to coordinate further referrals. Additional pediatric subspecialty consultations often include a neonatal intensivist, a pediatric nephrologist, and a pediatric urologist.

Radiologist

Establishing the diagnosis is a priority in the newborn period. VCUG with proper views of the posterior urethra should be obtained. Other required studies include renal US and, at times, renal scintigraphy.

Urologist

In the newborn period, the first treatment intervention is achieving bladder drainage. Catheterization may be difficult or even impossible because of the thickness of the valves or dilation of the posterior urethra with a hypertrophied bladder neck. Cystoscopic visualization with incision of the valves should be accomplished in the first few days of life, once the child is metabolically stable.

After the initial newborn period and successful bladder drainage, either by valve incision or by vesicostomy, long-term urologic care is needed. Renal deterioration secondary to progressive bladder dysfunction should be a primary goal and requires follow-up care with serial renal US and bladder urodynamic studies. Management is based on clinical findings, ranging from annual imaging to pharmacologic management to bladder reconstruction.

Nephrologist

Should the child display evidence of renal failure, input from a nephrologist is helpful in managing electrolyte imbalances, acidosis, and diet. In more severe cases, the nephrologist addresses dialysis issues and coordinates a possible renal transplantation.

Long-Term Monitoring

PUVs represent a lifelong disorder that can have a profound effect on the entire urinary tract. Accordingly, patients need periodic long-term urologic follow-up care. The status of the kidneys determines the need for additional specialty follow-up care (eg, with a pediatric nephrologist). Medications may be necessary for years to suppress symptoms of infection or enuresis. All of the medications listed in the Medication section are intended for long-term use.

Resolution of obstruction

Relief of bladder outlet obstruction is the first step in treatment. After incision of the valves, a repeat VCUG or repeat cystoscopy 1-3 months later confirms valve resolution and urethral healing. These patients may also be at risk for subsequent urethral stricture formation; repeat these studies at any point in the future if any recurrent bladder outlet obstruction symptoms are reported.

Urodynamics

Long-term changes, which can lead to elevated intravesical pressures, may occur in the bladder of patients with PUV. This leads to upper tract changes, urinary incontinence, and recurrent UTI. These patients may need periodic urodynamic studies to determine bladder capacity, compliance, and postvoid residual urine volumes (cystometrography).

In older children, uroflow and bladder scanning may be a less invasive way to monitor bladder dynamics. Noninvasive monitoring with voiding diary, uroflowmetry, US evaluation of residual urine, and serum creatinine measurement is acceptable, with more invasive cystometry and pressure/flow studies being reserved for those patients who manifest progressive deterioration.[33]

Upper tract changes

Patients may have baseline renal dysplasia. Elevated bladder pressures and recurrent UTI further may compromise renal function. Obtain periodic renal sonograms and serum creatinine levels. The frequency of these studies is determined by the severity of the renal and bladder dysfunction.

Urinary incontinence

Approximately one third of patients with PUVs have problems with diurnal enuresis when older than 5 years. Diurnal enuresis may be caused by the bladder changes that lead to elevated storage pressures and poor emptying. Rarely, sphincteric dysfunction secondary to valve ablation can be present. Treatment includes anticholinergic medication, CIC, and, in some patients, bladder augmentation.

 

Medication

Medication Summary

Posterior urethral valves (PUVs) initially represent a surgical condition. However, long-term treatment often comprises a combination of medical and surgical treatment, primarily directed at the bladder. The primary medications involved in bladder management are anticholinergic medications used to improve bladder compliance. Other medications that may be needed include prophylactic antibiotics and medications used in the management of renal insufficiency.

Anticholinergic agents

Class Summary

These agents are used to improve bladder capacity and compliance in the patient with elevated detrusor pressures, which may cause hydronephrosis, UTI, or incontinence. Early use of anticholinergic therapy has been associated with improved bladder function in infants with high voiding pressures and low storage volumes.[24]

Oxybutynin chloride (Ditropan)

Inexpensive and effective, oxybutynin chloride long has been the first-line anticholinergic. By inhibiting muscarinic action of acetylcholine on smooth muscle, exerts antispasmodic effect on bladder muscle. Its nonselective anticholinergic action increases adverse effects; however, it may produce fewer adverse effects if dosing is gradually increased over >2 wk. Available in both 5-mg tab and 5-mg/5-mL elixir. A long-acting 10-mg tab with once-a-day dosing was recently introduced but is expensive and has been approved only for adults.

Hyoscyamine sulfate (Levbid, Levsin)

Works by inhibiting postganglionic cholinergic receptors on smooth muscle cells. Rapidly absorbed and distributed throughout body, including across blood-brain barrier. Half-life is 3.5 h; excreted unchanged in urine.

Available in PO, IV, and SL forms; tab generally used for treatment of PUV. Time-release formulation available. Elixir and drops available.

Tolterodine (Detrol)

A new antimuscarinic drug with more selective receptor profile targeted for detrusor smooth muscle. Used extensively in adults but not approved by FDA for children. In adults, demonstrated equal in efficacy to oxybutynin chloride with significantly fewer adverse effects. Available in 1- and 2-mg tab.

Antibiotics

Class Summary

Patients with history of recurrent UTI may benefit from antibiotic prophylaxis, especially in the presence of vesicoureteral reflux. The ideal antibiotic for urinary prophylaxis is safe, effective, inexpensive, and has no adverse effects. Although no antimicrobial is ideal, some are preferred in children. Prophylactic dosage is usually one quarter of the therapeutic dose administered once per day. Too high a dose increases adverse effects (eg, GI upset) and may alter fecal flora. More appropriate antibiotics in children include trimethoprim (TMP), sulfamethoxazole (SMZ), nitrofurantoin, and amoxicillin. In addition, antibiotic therapy may lead to bacterial resistance, which may reduce options in the treatment of infection.

Trimethoprim and sulfamethoxazole (Bactrim, Septra, Cotrim)

Inhibits bacterial growth by inhibiting synthesis of dihydrofolic acid. TMP alone or in combination with SMZ is the most commonly used antibiotic for both treatment and prophylaxis of UTI. Inexpensive and has minimal adverse effects on bowel and vaginal flora because excreted and concentrated in urine. Pediatric susp (40 mg TMP and 200 mg SMZ per 5 mL) available.

Nitrofurantoin (Furadantin, Macrodantin, Macrobid)

Synthetic nitrofuran that interferes with bacterial carbohydrate metabolism by inhibiting acetylcoenzyme A. Bacteriostatic at low concentrations (5-10 mcg/mL) and bactericidal at higher concentrations.

Another common prophylactic antimicrobial agent, which is also excreted in urine, allowing urinary levels to be high while having few effects on fecal flora. Inexpensive and comes in both liquid and tab preparations. Rarely, associated with peripheral neuropathy and pulmonary hypersensitivity. SR formulation available; liquid susp (25 mg/5 mL) also available.

Amoxicillin (Trimox, Amoxil)

Interferes with synthesis of cell wall mucopeptides during active multiplication, resulting in bactericidal activity against susceptible bacteria. Used as prophylaxis in certain PO, GI, or genitourinary procedures.