Posterior urethral valves (PUV) are extra flaps of tissue in the urethra—the tube that runs between the bladder and the tip of the penis—that prevent urine from draining out of the bladder and through the urethra. This urinary tract obstruction begins during male fetal development early in pregnancy and only affects one out of every 8,000 baby boys. It has no known cause or genetic link.
PUV (also known as blocked urethral valves) can cause a range of health problems from mild to severe, depending on the degree of obstruction in the urethra. Symptoms of PUV are usually detected in a fetus during pregnancy. Babies with PUV usually develop hydronephrosis, or swelling of the bladder and kidneys and is seen on a prenatal ultrasound.
After such results, doctors begin to routinely monitor the fetus because of potential effects on fetal development. Babies need an ample amount of amniotic fluid for protection in the womb, but amniotic fluid does much more than that; it also promotes growth of the respiratory system by moving in and out of the lungs. At around 20 weeks of gestation, the majority of a baby’s amniotic fluid comes from urine that leaves a baby’s body. In severe cases, the obstruction caused by PUV can affect a baby’s ability to pee normally and reduce the amount of protective amniotic fluid. As a result, the lungs and overall fetal growth may be underdeveloped.
In severe cases, PUV can also cause irreversible ureter, bladder and kidney damage that requires lifelong care. This damage occurs as a result of higher levels of pressure when the bladder fills and empties. An obstruction can also cause the walls of the bladder to become unnaturally thick.
Some boys have symptoms of PUV during fetal development without any significant or lasting problems. In fact, boys occasionally have such mild effects from PUV that their symptoms do not surface until they are 7 to 10 years old and they begin to have frequent urinary tract infections, painful urination or problems with continence. In other cases, the severe effects of blockage of the urinary tract are obvious at birth and must be treated before they cause further damage that affects continence and proper function of the kidneys.
Diagnosis of Posterior Urethral Valves
After a prenatal ultrasound identifies swelling of the kidneys, ureter and/or bladder, mothers are often referred to a maternal-fetal specialist to monitor their baby’s condition in the womb. If you are referred to Riley at IU Health for such follow-up care, your baby will be checked frequently to make sure he has an adequate supply of amniotic fluid and to monitor the degree of swelling in the kidneys. Our expert physicians will also order routine ultrasounds and blood tests to watch how your unborn child’s lungs are developing. Often, a clear diagnosis is not made until after birth, when doctors can run more extensive tests, including:
- Renal ultrasound. This test looks at the baby’s development and assesses the bladder’s shape and degree of thickness and swelling, and the degree of kidney swelling.
- Blood tests. Your child's doctor will perform a blood test to measure kidney function and see how well infants excrete creatinine—a waste product that results from the kidneys doing their work.
- Voiding cystourethrogram (VCUG). In this test, contrast dye is injected into a bladder catheter and allows the doctor to see any vesicoureteral reflux—the amount of urine that backs up into the kidneys. This test provides the most definitive diagnosis of PUV in infants and can help determine the cause of recurrent urinary tract infections in young boys who are symptomatic for the first time.
- Mercaptoacetyltriglycine (MAG3) renal scan. This diagnostic nuclear medicine test that allows your child’s doctor to see his/her kidneys and learn more about how they are functioning.
- Renal scan. This is a nuclear scan to check kidney function and the ability of the kidneys to drain.
- Urodynamic studies. These assess how the bladder empties and stores urine.
Once these tests are done, we can begin planning treatment for any obstructions.
Most babies do not need treatment until after they are born, but this is not always the case. Occasionally, the effects of an obstruction may be severe enough to require treatment of the fetus during pregnancy. In such a case, a maternal-fetal specialist may encourage you to consider a procedure that inserts a vesicoamniotic shunt from your baby’s bladder to the amniotic space. A shunt is a soft tube that allows the bladder to drain urine and collect as protective amniotic fluid around the baby.
Other possible prenatal therapies include a short course of steroid treatment to help a baby’s lungs mature before birth. If a baby appears to be in respiratory distress or the lungs are not maturing well enough, an early delivery may be advised. If necessary, our team of maternal-fetal, neonatal and pediatric experts can carefully plan a birth that allows babies to receive immediate treatment for the obstruction and care for any respiratory emergency.
As soon as a baby boy affected by PUV is delivered, our primary concern is how well he can breathe independently. Babies with breathing problems are placed on a respirator until their lungs develop better and they can breathe on their own. Once their breathing issues are controlled, we begin to treat valve obstruction by inserting a catheter in the bladder. The purpose of the catheter is to bypass the valve obstruction and keep the bladder draining until we can fully evaluate each child.
In the first few days after birth, a multidisciplinary team of Riley at IU Health pediatric urologists, nephrologists and radiologists work together to assess each child’s anatomy and the severity of his obstruction.
If an infant is well enough, endoscopic surgery can be performed during the first few weeks of life. Our pediatric urologists insert a small scope through the urethra to disrupt the valves, allowing the bladder to drain normally.
In rare cases, a child’s anatomy may be too small for endoscopic surgery. If so, we can perform a vesicostomy, a procedure that brings the bladder up to the level of the skin somewhere between the belly button and the pelvic bone. This surgery is a stopgap measure, allowing the bladder to drain into the diaper until a child’s body matures enough to allow endoscopic surgery.
Some children have such mild cases of obstruction that they are treated once and have little or no health consequences afterwards. The more serious the obstruction and damaging effects on the urinary tract, the more likely the child will need further care and/or treatment by a pediatric urologist and/or a nephrologist. In the most serious cases, children may require lifelong care to monitor their renal function and their ability to pee.
Children who are affected with severe kidney damage may need routine peritoneal dialysis—a method of cleaning the blood that uses the lining of the abdomen. A catheter is inserted into the abdomen and the belly is flushed with special fluids designed to absorb the waste. Afterwards, the fluid is drained from the body. These children will need to undergo a kidney transplant at some point.
There is a wide spectrum of possible health consequences related to PUV. Whether your son’s condition is mild or serious, Riley at IU Health is a nationally-recognized resource, offering your family advanced maternal-fetal and pediatric specialty care from fetal development through birth and adulthood. We can support your child with precise diagnosis, proven treatments and any needs your son may have for ongoing care as a result of this rare urinary tract condition.
Key Points to Remember
Key Points to Remember
- Posterior urethral valves (PUV) are extra flaps of membrane in the urethra that prevent urine from draining normally out of the bladder and through the urethra—the tube that runs between the bladder and the tip of the penis
- This obstruction begins during male fetal development early in pregnancy and only affects one out of every 8,000 baby boys.
- Babies with PUV may develop hydronephrosis, or swelling of the urinary tract organs that is obvious on a prenatal ultrasound.
- PUV can restrict a baby’s healthy development in the womb, affecting its respiratory system and overall growth.
- Early treatment can prevent possible damage that can occur to a baby’s kidneys, bladder and urethra as a result of PUV.
Support Services & Resources
Support Services & Resources
This professional association for pediatricians shares public health information about posterior urethral valves.
This resource gives more information about posterior urethral valves and other conditions that can cause urinary blockages in newborns.
Fetal Center at Riley Children's Health
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