What is a Posterior Urethral Valve (PUV)?
A posterior urethral valve (PUV) is a leftover flap of fetal tissue that is located in the urethra. The urethra is the tube that carries urine from the bladder out of the body. PUV develops during the early weeks of pregnancy. It affects boys only.
A PUV causes problems during pregnancy because it blocks (or partially blocks) the flow of the baby’s urine from the bladder. This can cause the organs of the urinary tract to be swollen. This can cause mild to severe damage to the bladder, kidney and ureters (the tubes that carry urine from the kidneys to the bladder).
Another problem caused by PUV during pregnancy relates to the fluid around the baby in the mother’s womb (amniotic fluid). By about the 18th week of pregnancy, amniotic fluid mostly consists of the baby’s urine. PUV blocks the flow of urine. This results in a less-than-normal amount of amniotic fluid in the womb, which can interfere with normal lung development.
After the baby is born, a urology doctor can remove the PUV. However, the bladder and kidney damage that happened before birth can cause lifelong problems. Boys born with PUV often need to have follow-up medical care for the rest of their lives.
What Causes PUV?
Posterior urethral valve occurs by chance. It is not caused by anything a mother did or did not do during pregnancy. Sometimes, the condition is seen in twins, non-twin siblings, and fathers and sons. This suggests that in some boys with PUV, there is a genetic component.
PUV is a type of bladder outlet obstruction. It affects 1 in 8,000 boys a year worldwide, and about 500 babies a year total in United States.
When is PUV diagnosed?
If an unborn baby has severe PUV, some signs of the condition may show up on a routine prenatal ultrasound. Doctors cannot know for sure whether the baby has PUV until after the baby is born.
If your doctor suspects that your unborn child may have PUV, he or she may refer you to a fetal care center so that specialists can monitor you and your baby. Prenatal treatment may be available. Learn about the Cincinnati Children's Fetal Care Center.
Mild to moderate PUV may go undetected until later in life, when symptoms appear. These symptoms can include urinary tract infections or difficulty toilet training.
What are the signs and symptoms of PUV?
Before a baby is born, an ultrasound may show signs of PUV. These include swelling of the kidneys, a large bladder or a less-than-usual amount of fluid around the baby.
After the baby is born, a child with PUV may have some or all of these symptoms. PUV symptoms can appear when the child is a baby or much later in childhood.
- Repeated urinary tract infections
- Difficulty urinating, painful urination or a weak urine stream
- Poor growth and slow development
- High blood pressure
- Difficulty toilet training
- Bedwetting accidents past the usual age of toilet training (i.e., in children older than seven)
These signs also may be present in children who have been diagnosed with PUV but are not receiving effective medical care.
PUV can be diagnosed as mild, moderate or severe. This depends on the severity of PUV and how it affects kidney and bladder function.
What tests are used to diagnose PUV?
The care team uses a few different tests to diagnose and monitor PUV after the baby is born.
- Voiding cystourethrogram (VCUG) is a test that uses X-rays to take pictures of the urinary system. It shows the shape and size of the bladder and urethra, and any urine that is backed up to the kidneys. This test also shows how well the bladder empties urine.
- Renal bladder ultrasound (RBUS) is used to look at the child’s kidneys and bladder. This test uses sound waves to see the size of the kidneys, the degree of swelling in the kidneys and see the shape of the bladder.
- Blood tests help the care team check how well the kidneys are working.
How is PUV treated?
The most important treatment after the baby is born is to drain the bladder to take pressure off the kidneys. The bladder can be drained with a catheter or tube. Then when the baby is bigger, the PUV can be removed with surgery. Surgery will not fix any damage already present in the kidneys caused by PUV. But surgery can help prevent new damage to the kidneys and bladder.
The pediatric urologist will use one of the following surgical techniques to manage the PUV:
- Valve ablation involves inserting a cystoscope, a small telescope with a light and a camera lens at the end, into the urethra. During this procedure, the surgeon will be able to see the PUV and cut the valve so that it no longer blocks the flow of urine.
- Vesicostomy can help when there is a severe obstruction or when a baby is too small to have a valve ablation. A vesicostomy creates an opening from the bladder to the belly so that urine can drain all the time from the belly opening. This lowers pressure on the kidneys. The vesicostomy is a temporary treatment and can be closed in the future.
- Ureterostomy is a less common procedure. The ureter is disconnected from the bladder and connected to an opening on the belly. This way, urine can drain all the time from that opening. This procedure takes pressure off the kidney and lowers the risk of urinary tract infections.
Children with PUV need ongoing care from a team of specialists. The team should include specialists in neonatology, pediatric urology, nephrology, developmental pediatrics, nutrition and psychology.
The care team will provide a personalized care plan for your child and will watch your child’s kidney and bladder function, growth, development and other concerns. This can involve clinic visits and tests, such as ultrasound. Some patients need medicines, bladder drainage options or additional surgeries.
What medical complications are associated with PUV?
Some children do not have serious complications from PUV. But children with severe PUV could have:
- Loss of kidney function and an inability to make normal urine. These children will make three to four times the normal amount of urine each day. This places them at constant risk for dehydration if they are unable to keep up with their body’s fluid needs. These children are constantly thirsty.
- Bladder dysfunction
- Severe hydronephrosis (swelling of the kidneys)
- Breathing problems due to immature lungs
- Vesicoureteral reflux (when urine flows backwards from the bladder up to the kidneys). About 50 percent of boys with PUV will develop this condition.
- In about half of children with reflux, the condition can be treated with valve ablation (see “How is PUV treated?” above).
- In other cases, reflux may be treated with bladder management or anti-reflux surgery, also known as ureteral reimplantation.
Between 15 and 20 percent of people with PUV develop a condition called kidney failure. This can occur before the child is born, during the first few weeks of life, or later in life. When this happens, the child will need dialysis or a kidney transplant. Timely and proper bladder management may help slow down or prevent kidney failure.
What is the long-term prognosis for children with PUV?
Children with PUV need expert medical care from a multidisciplinary team of specialists for the rest of their lives. This is especially important if their PUV is moderate to severe. With this kind of care, many people with PUV will have normal bladder and kidney function, normal sexual development and fertility, and a good quality of life.,/p>
