Posterior urethral valves

Posterior urethral valves (PUV) also referred as congenital obstructing posterior urethral membranes (COPUM), are obstructive membranes that develop in the male infants urethra (tube that drains urine from the bladder) before birth (congenital) that blocks urine from flowing freely from the bladder to the outside of the body ¹⁾. The posterior urethral valve can obstruct or block the outflow of urine through the urethra. When this occurs, the bladder, ureters and kidneys become progressively dilated, which can lead to damage. The degree that the urine is blocked will determine the severity of the urinary tract problems.

Posterior urethral valves are the most common cause of chronic kidney disease due to bladder outlet obstruction in male children ²⁾. Posterior urethral valves are thought to develop in the early stages of fetal development.

Posterior urethral valves (PUV) affects only male infants and occurs in about 1 per 8000 to 1 per 25,000 male live births with a higher rate of occurrence in utero ³⁾. Posterior urethral valves is usually sporadic (occurs by chance). However, some cases have been seen in twins and siblings, suggesting a genetic component ⁴⁾.

In a study of referrals of boys diagnosed with suspected or confirmed posterior urethral valve in the United Kingdom and Ireland, the calculated annual incidence of posterior urethral valve was 1 in 3800 ⁵⁾. 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.

Posterior urethral valves are usually diagnosed before birth or at birth when a boy is evaluated for antenatal hydronephrosis. Before the era of antenatal ultrasonography, posterior urethral valves were discovered during evaluation of urinary tract infection (UTI), voiding dysfunction, or renal failure. Although rare, adult presentation of posterior urethral valves has been described in case reports, with symptoms ranging from obstructive voiding symptoms to postejaculatory dysuria. In the pre-ultrasonography era, a late presentation of posterior urethral valve was considered a good prognostic indicator suggestive of a lesser degree of obstruction.

Posterior urethral valve 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 ⁶⁾.

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.

Treatment of posterior urethral valves 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 ⁷⁾. 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.

Medical management relates to treatment of the secondary effects of the posterior urethral valves. Patients and families must also realize that medications, such as anticholinergics and suppressive antibiotics, are for controlling the symptoms of posterior urethral valve and are not curative.

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.

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 posterior urethral valves 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.

Figure 1. Normal urinary bladder anatomy of males

Figure 2. Congenital posterior urethral valves

Posterior urethral valves types

Young’s original description divided posterior urethral valves into three types, as follows ⁸⁾:

• Type 1 valves representing folds extending inferiorly from the verumontanum to the membranous urethra (~95% of posterior urethral valves). Occurs when the two mucosal folds extend anteroinferiorly from bottom of verumonatum and fuse anteriorly at lower level. A type 1 posterior urethral valve 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 2 – Bicuspid valves as leaflets radiating from the verumontanum proximally to the bladder neck.
• Type 3 – Valves as concentric diaphragms within the prostatic urethra, either above or below the verumontanum (~5% of posterior urethral valves). Type 3 posterior urethral valves are observed as a membrane in the posterior urethra believed to originate from incomplete canalization between the anterior and the posterior urethra.

Most pediatric urologists now regard the existence of type 2 posterior urethral valves as doubtful.

Figure 3. Congenital posterior urethral valves types

[Source ⁹⁾ ]

Posterior urethral valves causes

A posterior urethral valve 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.

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 posterior urethral valves 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 ¹⁰⁾. 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 posterior urethral valves 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 posterior urethral valves in approximately 10-15% of children undergoing renal transplantation, and approximately one third of patients born with posterior urethral valves 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 posterior urethral valve may be susceptible to incontinence, infection, and progressive renal damage.

As patients with posterior urethral valve age, bladder decompensation may develop, resulting in detrusor failure and increased bladder capacity. Many boys with posterior urethral valve 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 ¹¹⁾. 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 posterior urethral valve ¹²⁾.

Associations

Posterior urethral valves are also seen in association with other congenital abnormalities including ¹³⁾:

• chromosomal abnormalities, e.g. Down syndrome ¹⁴⁾
• bowel atresia
• craniospinal defects.

Posterior urethral valves prevention

Because posterior urethral valve 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.

Posterior urethral valves symptoms

Posterior urethral valves occur in varying degrees from mild to severe. Due to increased use of prenatal imaging, posterior urethral valves may be identified before any symptoms are present. If any dilation (hydronephrosis) is identified, your baby will be monitored throughout the pregnancy and after birth. Once your baby is born, further imaging studies will confirm the diagnosis.

Children who are diagnosed later may have the following signs or symptoms that require treatment:

• Urinary tract infection (UTI)
• Weak urine stream
• Difficulty with urination
• Urinary frequency
• New onset of urinary incontinence.

Physical examination

Most patients with posterior urethral valve 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)
• 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 an unreliable sign. A large lower abdominal mass may represent a markedly distended urinary bladder.

Posterior urethral valves diagnosis

Your doctor will use voiding cystourethrogram (VCUG) to diagnose posterior urethral valves. During this test, a catheter (tube) is placed through your child’s urethra into the bladder. The tube will be used to slowly fill the bladder with a solution called contrast. While the bladder is being filled, a special machine (fluoroscopy) is used to take pictures. The radiologist looks to see if any of the contrast goes back up into the kidneys. This study is used to diagnose vesicoureteral reflux (VUR). Additional pictures are taken while your child is urinating. The radiologist will look at the urethra while urine is passing to identify the blockage (posterior urethral valves).

Your doctor will also look at your child’s kidneys and bladder with a renal bladder ultrasound. This procedure uses sound waves to outline the kidneys and bladder. It will enable us to see the degree of hydronephrosis and the shape of the bladder.

Your doctor may also order blood tests to check how well the kidneys are functioning.

Antenatal diagnosis

The widespread use of antenatal ultrasonography has enabled diagnosis of posterior urethral valves 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 ultrasound, some patients with posterior urethral valves do present later in life.

In 1989, Thomas ¹⁵⁾ reported that 10% of patients with antenatal hydronephrosis detected by ultrasound had posterior urethral valves. In a 1993 report, Dinneen et al ¹⁶⁾ reported the sensitivity of antenatal ultrasonography to be only 45% in detecting posterior urethral valves in 45 patients who presented when younger than 6 months. With improvements in technology, the sensitivity has increased over the last 10 years.

Patients who have posterior urethral valves that are not diagnosed on antenatal ultrasonography and who do not present with overt urinary pathology are at risk for delayed presentation of posterior urethral valves.

Delayed presentation

Indicators of possible posterior urethral valves later in childhood include the following ¹⁷⁾:

• Urinary tract infection (UTI)
• Diurnal enuresis in boys older than 5 years
• Secondary diurnal enuresis
• Voiding pain or dysfunction
• Abnormal urinary stream

Posterior urethral valves 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 ¹⁸⁾.

Posterior urethral valves 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 posterior urethral valves.

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.

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.

Voiding cystourethrogram (VCUG)

The key to the workup of any child with antenatal hydronephrosis is voiding cystourethrography (VCUG). Voiding cystourethrogram (VCUG) is the best imaging technique for the diagnosis of posterior urethral valves. The diagnosis is best made during the micturition phase (voiding phase) in lateral or oblique views, such that the posterior urethra can be imaged adequately ¹⁹⁾.  Cycling the bladder during the study several times improves the sensitivity of the evaluation.

The diagnosis of posterior urethral valve 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. Diverticula, cellules, vesicoureteral reflux (VUR), and reflux into the ejaculatory ducts secondary to elevated bladder and urethral pressures may also be present.

Figure 4. Voiding cystourethrography (VCUG) posterior urethral valves

Footnote: Note hypertrophied bladder neck and dilated posterior urethra proximal to valve narrowing.

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.

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 posterior urethral valve 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 posterior urethral valves)

Multiple techniques are described for posterior urethral valve 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⁾.

Posterior urethral valves treatment

Treatment for posterior urethral valves depends on the severity of the condition, your child’s age, bladder and kidney status. The surgical goal is to preserve kidney and bladder function.

• Valve ablation: Once posterior urethral valves are identified, they need to be surgically incised. During valve ablation, the urologist will insert a cystoscope, a small device with a light and a camera lens at the end. He will use this instrument to make incisions in the valves so they collapse and no longer obstruct the urethra.
• Vesicostomy: In a situation where your baby is too small to undergo valve ablation or when a severe obstruction is noted, a vesicostomy may be recommended. A vesicostomy provides an opening to the bladder, so that urine drains freely from the lower abdominal opening. During surgery, a small part of the bladder wall is turned inside out and sewn to the abdomen. It looks like a small slit, surrounded by pink tissue. The vesicostomy is a temporary option and can be closed in the future.

After successful bladder drainage, either by the valve ablation or vesicostomy, your child’s doctor will continue to monitor your child’s condition throughout his childhood and adolescence. Your child’s doctor will need to assess the kidney function, watch for kidney growth and see how your child does through toilet training. Some children need ultrasounds every year while others may benefit from medications and additional surgeries.

Newborn care

In newborns with posterior urethral valves, 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 posterior urethral valves 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⁾.

Approximately one third of patients with posterior urethral valves 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 posterior urethral valve. 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 ²³⁾. 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 posterior urethral valve varies according to age, bladder status, and renal status. Antenatal surgery has been reported in patients diagnosed with posterior urethral valve 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 raised hopes that earlier intervention with vesicoamniotic shunting would improve postnatal renal function ²⁴⁾. 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 ²⁵⁾ found that vesicoamniotic shunting 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. The precise role of antenatal intervention remains to be established.

Urinary drainage

Postnatal primary valve ablation

Ideal treatment involves transurethral incision of the posterior urethral valve 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 ²⁶⁾. 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 ²⁷⁾.

In a study by Shirazi et al ²⁸⁾, factors significantly associated with a higher incidence of obstructive remnant leaflets after valve ablation for posterior urethral valve included the following:

• 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 clean intermittent catheterization (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 posterior urethral valve patients who undergo kidney transplantation, though it is associated with a higher incidence of recurrent urinary tract infection (UTI) ²⁹⁾.

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 posterior urethral valves, 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.

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.

Long-term monitoring

Posterior urethral valves 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.

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 posterior urethral valve. 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 posterior urethral valves 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, clean intermittent catheterization (CIC) , and, in some patients, bladder augmentation.

Posterior urethral valves complications

Pulmonary hypoplasia secondary to intrauterine renal dysfunction and oligohydramnios is the primary cause of patient death ³⁰⁾. Other complications of posterior urethral valve 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 posterior urethral valve 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 clean intermittent catheterization (CIC) have been identified as predictive of eventual renal deterioration ³¹⁾.

Vesicoureteral reflux

Vesicoureteral reflux (VUR) is commonly associated with posterior urethral valves 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 posterior urethral valve, reflux is generally secondary to elevated intravesical pressures. Therefore, the treatment of VUR in patients with posterior urethral valves involves treatment of intravesical pressures using anticholinergics, timed voiding, double voiding, intermittent catheterization, and, at times, bladder augmentation.

Urinary tract infections

Recurrent urinary tract infections (UTIs) are common in patients with posterior urethral valves. Elevated intravesical pressures predispose patients to infection, possibly by altering urothelial blood flow. Additionally, patients with posterior urethral valve 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 clean intermittent catheterization (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.

Posterior urethral valves prognosis

Over the past 30 years, the prognosis of boys with posterior urethral valves has steadily improved. In the past, most children were found to have posterior urethral valves only after presenting with urosepsis or progressive renal insufficiency. Older series demonstrated mortality figures approaching 50% by late adolescence ³²⁾. Today, most individuals with posterior urethral valves are discovered when antenatal ultrasound 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% ³³⁾.

Pposterior urethral valvess are the cause of renal insufficiency in approximately 10-15% of children undergoing renal transplant, and approximately one third of patients born with posterior urethral valves progress to end stage renal disease (the last stage (stage 5) of chronic kidney disease) in their lifetimes. Early initial presentation, pneumothorax, bilateral vesicoureteral reflux (VUR), and recurrent urinary tract infections (UTIs) after valve ablation are all associated with risk for progression to end stage renal disease (ESRD) ³⁴⁾.

As the child grows, renal metabolic demand increases proportionately. Failure of creatinine to drop 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 end stage renal disease (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 vesicoureteral reflux (VUR). The high-grade vesicoureteral reflux (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 ³⁵⁾. In the long run, VUR dysplasia (VURD) syndrome may not have the favorable outcome it was once thought to have.