What are posterior urethral valves?
Urethral valves occur when a boy is born with extra flaps of tissue that have grown in his urethra, the tube through which urine exits the urinary tract. This extra tissue prevents the urethra from properly carrying urine from the bladder to the tip of the penis and out of the body. When urine can’t be normally expelled from the body, the organs of the urinary tract (the kidneys, ureters, bladder, and urethra) may become dilated, or swollen. If this dilation occurs, it may cause serious damage to the tissues and cells within those organs.
What are anterior urethral valves?
The two main types of urethral valves are posterior urethral valves and anterior urethral valves. Of the two, posterior urethral valves are much more common than anterior urethral valves. The severity of these disorders depends on the degree of obstruction in the urethra. Symptoms and care of anterior urethral valves are similar to that of posterior urethral valves.
What causes posterior urethral valves?
Urethral valves are congenital, which means that boys are born with these extra flaps of tissue. It’s still not clear what causes these disorders, but they are believed to occur early on in male fetal development and may have a genetic component. Normally, the flaps of tissue in the urethra are very small structures. Researchers suspect that during fetal development, the body sends signals that tell the tissue to stop growing or help the tissue decrease in size. In boys with posterior or anterior urethral valves, this signal never gets sent or picked up, which causes the tissue to keep on growing.
What are the symptoms of posterior urethral valves?
In mild cases of urethral valves, a boy’s symptoms may not surface until the age of 10 years or older. In more serious circumstances, they can present as hydronephrosis (severe dilation of the kidneys) in newborns. Symptoms of urethral valves can vary from child to child and may include:
- an enlarged bladder, which may be detectable through the abdomen as a large mass
- urinary tract infection
- painful urination
- weak urine stream
- urinary frequency
- bedwetting or wetting pants after your child has been toilet trained
- poor weight gain
- difficulty with urination
Severe cases can lead to the following medical complications:
- respiratory distress
- hydronephrosis (dilation of the kidneys)
- bladder dysfunction
- renal function impairment and an increased risk of kidney failure
- vesicoureteral reflux (when urine flows backwards from the bladder up to the kidneys).
How we care for posterior urethral valves
At Boston Children’s Hospital, we take a team approach to treating urethral valves. Your child will be evaluated and treated by a group of skilled specialists from many different disciplines, including nephrology, urology, and radiology. Depending on the severity of the abnormality, posterior or anterior urethral valves can be treated with various surgical interventions and medical management.
Since boys with urethral valves have an up to 25 percent chance of kidney failure over the course of their lifetime, our specialists in Boston Children's Department of Urology make maintaining optimal bladder function the primary goal of treatment. We will help your child prevent bladder function issues, incontinence, and urinary tract infections by regularly monitoring his kidney function, bladder functioning, and voiding ability (emptying of the bladder).
Posterior Urethral Valves | Diagnosis & Treatments
How are posterior urethral valves diagnosed?
Today, more and more cases of urethral valves are being detected during pregnancy through prenatal ultrasound. This early detection means that a baby's symptoms, and the posterior or anterior urethral valves themselves, can be treated before they become more serious or cause more injury. Although findings from prenatal tests can make doctors suspect posterior or anterior urethral valves, a formal diagnosis can only made after the baby is born.
Clinicians make a definitive diagnosis using:
- voiding cystourethrogram (VCUG), a minimally invasive test that uses special x-ray technology to examine the urinary tract and bladder
- direct endoscopic visualization (cystourethroscopy), a test that uses an endoscope (a small flexible telescopic tube with a light and a camera lens at the end) to examine the urethra
- blood tests to check for abnormalities such as elevated creatinine, a waste product that the body makes each day. Since it can only leave the body through the kidneys, a high creatinine level in the blood is a sign of decreased kidney functioning.
- urodynamic study (UDS), a test that involves evaluation of bladder storage and emptying function
How are posterior urethral valves treated?
In the majority of cases, urethral valves are treated with a surgical procedure called endoscopic incision of the valves. Also known as valve ablation or urethral valve ablation, this is a surgical technique that trims down excessive tissue of the valves. It is a minor and minimally invasive procedure, and only requires a small incision at the site of the ablation (removal) of the valves.
A newborn with hydronephrosis (dilation of the kidneys) may need the following surgical treatments:
- urinary diversion, a procedure that diverts the urine before it reaches the urethra. This is done with a vesicostomy, an operation performed on infants who are too small to undergo endoscopic valve ablation. This procedure creates an opening from the bladder to the outside of the body so the urine can drain directly into a diaper.
- proximal diversion, a less common procedure in which the ureter is brought out to the skin, allowing the urine to be brought out (diverted) to the side of the body. This procedure is done for boys with more severe presentations of the disease, for example, when there are very thick bladder walls or if the bladder itself shows marked abnormality.
Although medication alone can't treat urethral valves, it may be used in addition to surgery to treat more severe problems.
For example, the wall of the bladder has two layers: a soft inner lining and an outer layer of muscle. Some boys have severe hyperactivity of that muscle, which makes the bladder muscle stiff. These boys may benefit from medications that help relax and soften the bladder muscle.
The most common classes of medication used to help relax the bladder muscle include:
Even after surgery, your son may continue to experience mild symptoms of urinary incontinence, frequency, and urgency. A simple outpatient procedure can often cure these symptoms. If your child’s urinary tract is severely affected, extensive reconstructive surgery may be helpful in preventing damage to the kidneys. It’s essential that you keep in close contact with your son’s physician so that they can monitor your son for any sign of developing problems.
Ongoing medical management is very important for boys with urethral valves. Due to the varying degrees of severity, some boys will need to be followed more closely than others. For the most part, boys will need to be monitored for kidney function, bladder functioning, and voiding ability.
Generally, after the initial surgery is performed, your child will receive another voiding cystourethrogram (VCUG) to ensure that the appearance of the valves is gone or much less significant. Six months after the valves have been ablated, doctors will continue to monitor your child’s bladder function using a urodynamic study. This approach monitors bladder function and gives specific objective information about the bladder’s capacity, storage pressures, bladder (detrusor) muscle, and emptying function of the bladder.