Posterior Urethral Valves

What is Posterior Urethral Valves?

Posterior urethral valves are a leading reason for blockages in the urinary tract and long-term kidney disease in children. These valves are actually obstructive folds, like curtains that are stuck closed within the urethral tube. They can block the flow of urine and are exclusively found in boys.

This condition was first noted by Morgagni in 1717. Langenbeck also observed these valve-like folds in 1802, and their existence was confirmed by Hugh Hampton Young in 1919.

Posterior urethral valves can result in a wide variety of health problems. These may range from cases with no symptoms to severe conditions that can be life-threatening. Complications can include acute and chronic inability to urinate, kidney failure, bladder outlet obstruction, swelling of the kidneys and ureter tubes, urine flowing backward from the bladder into the kidneys, difficulty in urinating, and in severe cases, underdeveloped lungs due to reduced amniotic fluid.

Posterior urethral valves can be split into three subtypes based on Young’s criteria, which describe the placement of the valves within the urethra.

• Type I (95% of cases): The obstructive folds come from a structure called the verumontanum and block the urethral tube. These folds are leftovers from a structure called the Wolffian duct.
• Type II: Two leaflets or membranes are attached near the bladder neck, starting from the verumontanum. These are now considered as enlarged folds, and not a true case of posterior urethral valves.
• Type III (5% of cases): There is a round membrane at the verumontanum with a hole in the middle, which can be either above or below the verumontanum. The hole doesn’t directly connect to the verumontanum.

However, this classification has been disputed. Dewan suggested that the structures in types I and III might be the same, and they only appear different because a defect in the middle rupture before birth. He introduced new terms for posterior urethral valves, like congenital obstructive posterior urethral membrane and “Cobb’s collar.”

Congenital obstructive posterior urethral membrane is another term for the classic type of posterior urethra valves and is always associated with the verumontanum. This birth defect shows up as a potentially obstruction causing membrane with folds extending along the posterior urethral wall to the verumontanum.

Cobb collar is not a valve or a typical posterior urethral valve, but a birth defect related to an obstructive urethral stricture or membrane not associated with the verumontanum. It is located below the verumontanum in the urethra, separate from the verumontanum and the external urinary muscle. This anomaly is believed to be a lasting remnant of the urogenital membrane.

What Causes Posterior Urethral Valves?

Posterior urethral valves are a birth defect, but scientists are still debating what causes them during a baby’s development in the womb. Earlier theories suggested these valves might be due to continuous attachment of an area called the verumontanum (a small lump on the inside of the bladder) to the roof of the urethra (tube carrying urine out of the body) or due to a persistent urogenital membrane (a structure in an embryo’s development).

A study by a scientist named Stephens in 1955 proposed another theory. He thought posterior urethral valves might form because the ducts that help develop kidney and reproductive organs fail to properly combine with the urethra. This failure leads to a blockage in the urethra.

Research conducted by Dewan in the 1990s tried to resolve confusion between two theories: the congenital obstructive posterior urethral membrane (a blockage in the urethra present from birth) and the Cobbs collar (a particular defect in the urethra) theory. Results showed that Cobbs collar is likely due to the urogenital membrane persisting, while the congenital obstructive posterior urethral membrane might occur due to the verumontanum attaching to the roof of the urethra.

Normally, while a baby grows in the womb, a part of the duct becomes absorbed and a part of the structure that develops in the bladder in early stages. This happens at the place where the verumontanum will be formed at around 4 weeks into a pregnancy. That’s why all real posterior urethral valves are somewhat attached to the verumontanum. Usually, this process leaves small leftovers called the plicae colliculi.

Posterior urethral valves happen when there is an abnormal attachment or absorption of the ducts, or if the tissue between the verumontanum and the front wall of the tube that carries sperm and urine doesn’t go away as it should during development.

Risk Factors and Frequency for Posterior Urethral Valves

Posterior urethral valves, a condition that mainly affects male infants, has a varying incidence worldwide. It occurs roughly in 1 in every 5,000 live male births. About half of the people affected by this condition may develop a serious kidney disease, called end-stage renal disease (ESRD), within ten years.

In the United States specifically, this condition occurs in about 1 in every 4,000 to 8,000 live births, which equates to roughly 500 new cases each year. However, this number can differ depending on the country. For example, in Australia, during a 5-year review, the rate recorded was about 1 in 7,800 live births, while in the United Kingdom (UK) and Ireland, the incidence was higher at 1 in around 3,800.

• About one-third of the children diagnosed with posterior urethral valves may develop ESRD.
• Between 10% and 15% of all children who have a kidney transplant may have a history of posterior urethral valves.

In the UK, pre-birth detection of posterior urethral valves was seen in 35% of cases, and around 42% of cases diagnosed during infancy or the newborn period. In contrast, nearly 23% of cases were identified late when the child was 5 years or older.

Signs and Symptoms of Posterior Urethral Valves

Posterior urethral valves are diagnosed by studying a patient’s medical history and conducting a physical examination. Information considered includes prenatal ultrasound results, symptoms at birth, urinary habits, and related signs. Some common symptoms in newborns are being unable to urinate, having a swollen bladder, and facing difficulty breathing. During an examination, doctors check for signs of kidney and bladder dysfunction, like high blood pressure, poor growth, or noticeable bladder bulges. Other urinary issues, like undescended testicles and hypospadias (a urethra development issue), are also checked for.

Currently, many cases are identified during prenatal ultrasound checks. About 60% of babies prenatally diagnosed with posterior urethral valves will also show signs of kidney dysplasia, a condition where kidneys don’t develop properly. An early diagnosis indicates a high chance of complications but allows for early neonatal surgery to improve kidney and bladder function. An ultrasound may reveal a large bladder diverticulum, patent urachus, or a urinoma caused by urine leakage. Swift treatment can prevent further kidney damage and improve the outcomes for the baby.

Severe cases might cause newborns to suffer from respiratory distress, or breathing difficulties related to underdeveloped lungs, requiring immediate medical intervention. Babies that can’t urinate within 24 hours after birth should be checked for posterior urethral valves and other issues. Other symptoms that may occur are urinary tract infections (UTIs), failure to thrive, poor feeding, lethargy, urinary retention, and more.

Older children may also show similar symptoms. In rare instances, urinary ascites or a pooling of urine can occur following bladder or fornix rupture. In undiagnosed cases in children older than 5 years, bed-wetting during the day is often the first symptom, followed by UTIs, painful urination, weak urine flow, blood in the urine, protein in the urine, and kidney failure. More advanced cases may also reveal signs of kidney damage.

The most common symptoms in a child with posterior urethral valves include:

• Abdominal or lower back pain
• Swelling of the lower abdomen
• Bladder diverticula
• Developmental delays
• Difficulty or pain during urination
• Distended bladder
• Failure to thrive
• Frequent UTIs
• Blood in the urine (hematuria)
• Overfilled kidneys (hydronephrosis)
• Patent urachus
• Poor weight gain
• Urinoma due to a bladder perforation or a rupture in the fornix

Signs common in other conditions can also appear in neonates with posterior urethral valves. These may include signs like knee or elbow bent, dimpled skin, and distinctive facial features characteristic of Potter syndrome. Additional urinary anomalies like a palpable or distended bladder and non-urological anomalies, such as problematic vein drainage, lower limb deformities, Down’s syndrome, high blood pressure, and others, may also be identified. A thorough examination of these related anomalies is critical to effectively manage this condition and improve patient outcomes.

Testing for Posterior Urethral Valves

During pregnancy, ultrasounds can be used to examine the mother and her baby. Discovering things like a swollen bladder with thick walls and both kidneys being swollen in male infants before birth may suggest the child has something known as posterior urethral valves. However, this might not apply if the condition is detected after birth. Also, nearly a third of all cases of this condition may be diagnosed using ultrasound before birth.

On the other hand, a “keyhole” sign identified on an ultrasound could signal a urinary obstruction, which is often due to posterior urethral valves. But, recent studies have shown that this sign is mostly related to another condition called urethral atresia rather than posterior urethral valves, and therefore, it may not be a reliable sign for the latter.

Doing multiple scans is not only crucial for diagnosing during pregnancy but also for identifying warning signs such as low levels of amniotic fluid (which surrounds the baby in the womb) and evidence of abnormally-developed kidneys. As there could be reduced urine levels during the first week after birth naturally, repeat ultrasound examinations may be required. Ultrasound performed through the perineal approach (between the genitals and the anus) may reveal a narrowed back part of the urethra and valve leaflets.

Specialized tests can be used to check whether the baby’s kidneys are working properly. If everything is normal, the baby’s urine should show low tonicity with a measure of substances in the fluid of less than 210 mEq/L. High measures and elevated β-2 microglobulin levels above 4 mg/L could suggest irreversible kidney issues.

After birth, testing methods include blood tests, imaging, and urodynamic studies, which check how well the urinary system is working. In the first 48 hours after birth, the baby’s blood chemistry is mostly influenced by the mother’s levels. To get accurate results, blood for infant serum testing should be collected after this period.

Important blood tests include serum creatinine, BUN (which measures kidney function), and potassium levels for understanding the level of newborn kidney dysfunction and checking for a high level of potassium in the blood. Blood gas testing can be useful, especially if the child is unwell, since it helps determine if there is metabolic acidosis (a high level of acid in the body).

Assessing lung function is equally important. Some newborns may have underdeveloped lungs due to low amniotic fluid related to posterior urethral valves. This could significantly affect the newborn’s breathing and might need special medical interventions to support lung development and function.

Imaging Options

Ultrasounds of the kidneys and bladder are preferred as the first imaging choice because there’s no exposure to radiation for the baby, and it’s readily available and quick to perform. Additionally, it’s a straightforward method to identify various issues that might be related to posterior urethral valves in newborn boys, such as swelling of the kidneys, swelling and distension of the bladder, urinary retention, and an enlarged back part of the urethra (known as the “keyhole” sign).

Renal ultrasound can reaffirm suspicions from the pregnancy period, like hydroureteronephrosis, swollen and thick-walled bladder, and dilated posterior urethra. It can also measure kidney thickness and identify different layers of the kidney’s tissue. In older boys showing symptoms, ultrasound can be a handy tool for detecting similar findings linked to posterior urethral valves.

Some common ultrasound findings include:

* Swollen kidneys or ureters
* Dilated prostatic urethra (“keyhole” sign)
* Distended bladder with a thickened wall (>3 mm) with poor emptying over 30 minutes. (This might just be normal, so double-checking using other tests is recommended.)
* Fluid accumulation in the abdominal cavity of the fetus
* Focal renal-formatted cysts, which might hint at abnormal kidney development
* Low amniotic fluid (surrounding the fetus)
* Urinoma (swollen sac-like structure filled with urine)

Contrast-enhanced serial voiding ultrasound has emerged as a viable alternative to repeated voiding cystourethrograms to monitor patients with posterior urethral valves. This technique offers several benefits, including avoiding radiation exposure, high accuracy, and real-time imaging capabilities.

However, voiding cystourethrography remains the standard imaging tool for diagnosing posterior urethral valves. It’s important to note that even if it’s done correctly, a negative voiding cystourethrography cannot definitively rule out the diagnosis.

Because of these limitations and because of the discomfort they may cause for the patient, these scans are not always preferable. Hence, other methods, like ultrasounds and a medical procedure called cystoscopy, can provide more detailed and accurate information about the condition. Cystoscopy would be encouraged even if the voiding cystourethrography results are negative, provided there is enough suspicion of posterior urethral valves in the patient.

Renal radionuclide scans may also be used to assess functional differences between the kidneys and detect abnormalities in the kidney tissue. However, these scans have their limitations and are not recommended for routine use in newborns. Instead, a VCUG and ultrasound, which provide more precise information about posterior urethral valves, are preferred.

Finally, urodynamic studies help provide additional information about how well your child’s bladder and sphincters are working, this is especially crucial after the child had surgery for the posterior urethral valves. Such studies, repeated periodically, help track how the bladder function changes over time.

Treatment Options for Posterior Urethral Valves

Treating a condition called “posterior urethral valve” typically requires a collaboration involving newly born baby disease specialists (neonatology), kidney experts (nephrology) and specialized urinary system doctors (pediatric urology). Recognizing the condition early, preferably while the baby is still in the womb, and a quick response, are very important for the best outcome. The strategies used can include the removal of the blocked part of the urinary tract, changing the direction of urinary flow, and continuous monitoring to deal with any potential complications and ensure that bladder and the kidneys are functioning properly.

Prenatal Treatment

There are no proven guidelines for prenatal treatment in posterior urethral valve cases at present in the U.S., and its use is still being tested due to the risks involved. However, doctors should consider its use when the condition is detected by the second trimester of pregnancy, and the amount of amniotic fluid is severely low. Each country has different regulations for intervening depending on kidney function, but generally, before any intervention, the kidneys must be working well.

In the United Kingdom, prenatal intervention should be considered when kidney function is good, such as when levels of sodium, chloride, osmolality (the concentration of substances like salt and sugar in the urine), and a type of protein called β2 microglobulin are all within a certain limit. To analyze the urine, a needle is usually used to draw fluid from the fetus’s bladder.

Prenatal interventions might include various procedures to remove the obstruction and lessen the complications associated with this condition. These procedures might be the placement of a tube to allow flow between the bladder and amniotic sac, the creation of a surgical opening into the bladder, examining the bladder with an instrument, or the removal of the valve that is blocking the urinary tract. Each of these approaches has its pros and cons, and they all play a role in managing the condition and improving the outcome for the baby.

In a study of 40 patients, most (36) received prenatal intervention. Unfortunately, five babies born prematurely died mainly due to breathing trouble or complications related to the treatment. Of the surviving patients, many developed chronic kidney disease over time, and three required a kidney transplant.

In a randomized trial, called the PLUTO study, the efficiency of inserting a shunt into the fetus’s bladder was compared to the usual treatment for blocking of the lower urinary tract in fetuses. The trial recruited 31 women from the UK, Ireland, and the Netherlands. The results were inconclusive due to the small number of participants.

More recent studies show some improvements in the outcomes. In one, more than half of the patients who underwent a procedure called “fetal cystoscopy” survived up to one year old, with most of those showing normal kidney function at that time.

Prenatal interventions carry substantial risks and should only be performed during clinical trials or at specialized centers with expertise in these complex procedures. They might be an option for pregnancies where severe posterior urethral valves accompanied by severe oligohydramnios are diagnosed in the mid-trimester, and where the fetus is known to have good kidney function and normal chromosomes. Well-designed studies are needed to determine the best role of prenatal surgery in severe cases, and to figure out which surgical approach provides the best results.

Postnatal Treatment

After birth, treatment should focus on addressing immediate concerns such as imbalances of salts in the blood, hydration status, and the need for breathing support. A team of neonatologists, urologists, and nephrologists should work together to provide complete care. Once the baby has become stable, a decision can be made about further treatment options, such as surgery.

If the baby cannot pass urine, the bladder will need to be emptied. This is usually done with a catheter, a thin, flexible tube that’s inserted through the urinary tract into the bladder. Sometimes, a feeding tube may be used instead of a catheter.

If standard catheterization methods fail, alternative options might be required to ensure prompt and good urinary flow and prevent further harm to the urinary tract and to the kidneys. These options might involve the use of an ultrasound or fluoroscopy to guide these methods, which can be more complex and may include creating a surgical entrance into the bladder or other advanced techniques. If necessary, a catheter or feeding tube can be left in place for up to 4 weeks.

Once these immediate concerns have been managed, a definitive procedure like cystoscopic ablation can be considered depending on the baby’s overall health and stability, as well as the severity of the condition. Cystoscopic ablation involves looking into the bladder with a special scope and then using the scope to take out the valves that were causing the urine blockage. This procedure is currently the preferred initial definitive treatment.

After the surgery, management is usually based on results from tests that look at the bladder’s function, and clinical parameters. This often includes doing self-catheterizations, taking medicines such as alpha-blockers and anticholinergics, or a combination of those approaches. Regardless of the chosen treatment method, the patients will need continuous monitoring for chronic kidney disease.

Follow-up examinations are crucial to see how well the valve removal treatment was and how the patient is doing. One should have follow-ups of the urethra and bladder 3 months after the surgery, and then on a yearly basis. They are advised to assess kidney and bladder function and to monitor for development of any potential kidney diseases.

What else can Posterior Urethral Valves be?

When a doctor is considering a diagnosis of posterior urethral valves, there are several other medical conditions that can cause similar symptoms. These are:

• Anterior urethral valves
• Blockages at both points where the ureter and bladder meet (Ureterovesical junction stenosis)
• Abnormal contraction of the bladder muscles (Detrusor sphincter dyssynergia)
• Abnormal placement of the ureter that causes blockage (Ectopic obstructive ureteral implantation)
• Growth of noncancerous cells in the posterior urethra (Fibroepithelial polyp of the posterior urethra)
• Previous surgical removal of posterior urethral valves being incomplete
• Megalourethra (an abnormally wide urethra)
• An abnormally large bladder, or Megacystis, identified as over 7 mm at 12 weeks of pregnancy. In approximately 60% of cases, posterior urethral valves are the cause.
• Neurogenic or atonic bladder, which is a lack of bladder control due to a brain, spinal cord, or nerve problem
• Primary megaureter, a congenital condition where the ureter is abnormally dilated
• Prune Belly syndrome, a rare genetic disorder characterized by the partial or complete absence of abdominal muscles
• Ureterocele, a swelling near the bottom of one of the tubes (ureters) that carry urine from the kidneys to the bladder
• Urethral atresia, stenosis, or stricture which are different types of urethral blockages
• Vesicoureteral reflux, a condition that allows urine to go back up into the kidneys

The physician needs to consider all these conditions and perform appropriate tests to make a proper diagnosis.

What to expect with Posterior Urethral Valves

The outlook for posterior urethral valves, a condition that affects the normal flow of urine, can vary. This largely depends on the degree of blockage and any complications that occurred before birth. Research suggests that the levels of creatinine (a waste product that kidneys filter out) can indicate how well the bladder will function in the long term. If the creatinine levels are above 1 mg/dL during the first year of life, this could indicate a higher risk for End-Stage Renal Disease (ESRD) and kidney failure.

People diagnosed with posterior urethral valves before the 24th week of pregnancy, showing signs of abnormal kidney development, or severe bilateral hydronephrosis (a condition where both kidneys are swollen due to urine not draining properly), along with low amniotic fluid (oligohydramnios), aren’t likely to have a favorable outcome. They face a high risk of chronic kidney failure, ESRD, and early mortality. In fact, the mortality rate can be as high as 90% or more if oligohydramnios due to posterior urethral valves is identified during the second trimester of pregnancy.

Patients who have been diagnosed with posterior urethral valves before birth and show normal or unremarkable levels of amniotic fluid at 24 weeks of pregnancy usually have normal kidney function at birth. However, up to a third may need some treatment for kidney failure later in life.

Most babies who survive the newborn period often go on to develop chronic kidney disease, with many experiencing ongoing bladder issues. About 15% to 20% of patients with posterior urethral valves will progress to ESRD, but this could be as high as 29%. Several factors contribute to this risk, including a decreased rate of kidney filtration at 1 year of age, multiple urinary tract infections with fever, high starting levels of creatinine, and a renal volume (the size of the kidneys) below the third percentile. Surprisingly, a larger renal volume can protect against severe kidney failure. This implies that good kidney growth during development might help reduce the risk of severe kidney problems in patients with posterior urethral valves.

Surprisingly, the development of prenatal urinary extravasation, which is a condition where urine leaks into surrounding tissues, may help preserve kidney function in patients with serious posterior urethral valve disease. This shows the complex relationship between prenatal urinary dynamics and kidney outcomes in affected people.

Advances in prenatal ultrasound have enabled early detection of posterior urethral valves in the womb, which opens the door for surgical interventions before birth. However, despite aggressive treatments, no clear evidence has been found showing improvements in long-term outcomes and survival rates.

Early surgical treatment shortly after birth, alongside a comprehensive management plan which includes techniques to help empty the bladder, medication, proper use of antibiotics, and a routine for self-catheterization can offer the best protection against worsening bladder and kidney function. Regularly monitoring kidney function and bladder activity through follow-up examinations is crucial to ensure timely actions and adjustments to the management plan.

Possible Complications When Diagnosed with Posterior Urethral Valves

Complications from posterior urethral valves can lead to serious health problems and long-lasting health challenges. Generally, the degree of these complications differs from person to person, but they usually come from a urinary blockage due to abnormal valves. These issues can affect kidney function, bladder health, and overall quality of life. Knowing the risks is essential for early diagnosis, treatment, and care, which can lessen their impact and improve patient recovery.

Bladder Dysfunction

Research, involving 119 patients, showed that about one-third developed seriously abnormal bladder function after initially being treated with drainage and then an operation to remove the abnormal valves. As a result, these patients needed regular self-catheterization, with or without medications to manage their bladder issues.

Due to the large number of people experiencing these complications, it’s vital to include urodynamic studies in the ongoing treatment of patients with posterior urethral valves. Further research showed that up to 41% of patients showed signs of bladder dysfunction. However, out of 55 children who were toilet trained, 42 were able to control their bladder. Regardless, medications were used to help reduce leftover urine after voiding if needed after urodynamic studies.

Kidney Failure

A study including 274 patients who received their first treatment before being three months old in different hospitals, revealed that 16% required therapy to replace kidney function within ten years. These patients were categorized based on the lowest levels of creatinine recorded in the first year.

Vesicoureteric Reflux and Urinary Tract Infections

Because of high pressure in the bladder, at least one-third of patients diagnosed with posterior urethral valves will end up having vesicoureteric reflux. Generally, this condition is managed via antibiotics to reduce kidney damage, scarring, and infections. However, medications may also be used to help with voiding.

In cases where repeated urinary tract infections lead to kidney damage and severe reflux, which further hinders bladder emptiness, urinary reconstruction might be required. Even if vesicoureteric reflux isn’t present, patients with consistently increased leftover urine are prone to repeated infections due to urine stagnation. The risk is even higher in cases with enlarged upper urinary tracts.

Other potential complications of posterior urethral valves include:

• Chronic kidney failure
• ESRD
• Incomplete valve removal
• Incomplete voiding
• Incontinence
• Permanent bladder dysfunction
• Repeated UTIs
• Urethral strictures
• Vesicoureteral reflux

Preventing Posterior Urethral Valves

Posterior Urethral Valves, a urinary tract issue, can often cause complications even after the initial problem has been treated. As a result, patients might have to learn how to do clean intermittent self-catheterization. This is a technique where a tube is temporarily inserted into the bladder to drain urine, and can be done at home. Parents and later children need to be taught this skill to manage the condition properly. It’s very important for patients to understand their condition to manage it effectively and prevent chronic kidney disease, a long-term serious condition affecting the kidneys.

Arming patients with the right information about their condition helps them make the right decisions for their health, which is vital for dealing with any long-term health problems, like the posterior urethral valves. Regular check-ups with healthcare providers are important to keep track of how the condition is progressing and make necessary changes to the treatment plan if needed.