Years published: 2023
NORD gratefully acknowledges Gregory Cichon, MD candidate, Creighton University School of Medicine and Pramod Reddy, MD, Division Director, Pediatric Urology, Cincinnati Children’s Hospital, for the preparation of this report.
Posterior urethral valves (PUV) are a rare condition found only in boys where obstructing membranous tissue is present within the lumen of the posterior urethra. It is the most common cause of urinary tract obstruction in newborn males, occurring in 1 in 5,000 to 8,000 pregnancies or roughly 500 babies per year in the U.S. PUV is also the most common cause of chronic kidney disease (CKD) due to urinary tract obstruction in children. PUV can be suspected on prenatal imaging during the pregnancy, but it is only diagnosed after birth when imaging can be done on the child, including a bladder x-ray. PUV requires surgical treatment. There can be some residual bladder dysfunction that might require medical management.
Posterior urethral valves are blockages in the lower urinary tract of males. They are folds of residual tissue in the tube that carries urine out of the body (the urethra) and only occur in boys. These valves were first described by doctors in the 1800s. They can also cause problems in the upper urinary system as well as other parts of the body such as the lungs. It is important to realize that there can be ongoing changes to the urinary bladder even after the PUV have been surgically treated. It is important to diagnose and treat the condition as soon as possible to prevent long-term complications, such as kidney damage, urinary tract infections and poor growth and development.
Most cases of posterior urethral valves are found before birth during an ultrasound. Doctors look for things like swelling in the tubes that carry urine from the kidneys to the bladder (the ureters) and for a swollen thick-walled bladder that may not empty well. A low level of fluid around the baby or swelling in the baby’s belly may also be seen.
After birth, symptoms of PUV can vary. Affected boys may have trouble urinating or need to urinate often, get infections or have a swollen bladder. They may also be very tired, not want to eat or not grow well. In severe cases, they may have trouble breathing because their lungs didn’t develop properly. Older boys may present with slightly different symptoms such as urinary tract infections, bedwetting after being potty trained or other problems like high levels of waste in their blood.
Doctors can look for signs of PUV in babies by checking their belly for any swelling of the kidneys and/or the bladder.
The most common symptoms in a child with PUV include:
● Difficulty urinating (i.e., weak urine stream or dribbling of urine) or inability to urinate
● Frequent urinary tract infections
● Abdominal or lower back pain
● Blood in the urine
● Enlarged bladder or kidneys
● Swelling in the abdomen or genital area
● Frequent urination
● Poor weight gain or failure to thrive in infants and young children
● Urinary incontinence or leakage of urine
● Delayed development of physical and cognitive abilities in infants and children.
Posterior urethral valves form when a baby is still developing inside its mother, but the cause is not known. Some theories suggest it’s due to problems with the formation of the urinary system. More research is needed to pinpoint the exact cause.
PUV results from the formation of valve-like membranes from a tissue in the beginning of the urethra, near the base of the bladder. The valves can block the outflow of urine through the urethra, leading to damage in the bladder, ureters and kidneys. However, it is important to note that PUV occurs randomly by chance and is not caused by anything a mother did or did not do during pregnancy.
In the womb, if the baby is unable to urinate due to PUV, there might be a deficiency in amniotic fluid, known as oligohydramnios. A major concern for oligohydramnios is the lack of proper lung development, called lung hypoplasia. Therefore, management of a baby boy born with PUV may involve more than urinary support but also respiratory support.
PUV is rare, occurring in about 1 in 5,000 to 1 in 8,000 male infants. It is the most common cause of urinary tract obstruction in newborn males, occurring in roughly 500 babies per year in the U.S.
Posterior urethral valves are typically suspected during prenatal ultrasound and diagnosed with imaging after birth. Doctors look for signs like a swollen bladder, but it’s not always clear. If undetected during pregnancy, symptoms such as difficulty urinating, urinary retention and/or urinary tract infections in infants and young children may raise suspicion.
After birth, doctors can do blood tests to check for kidney problems. A urine sample may also be collected to test for infection or abnormalities.
To confirm PUV diagnosis, a healthcare provider assesses the child’s medical history and then performs a physical examination and imaging tests like bladder ultrasound or voiding cystourethrogram (VCUG). VCUG uses special dye and x-rays to identify the structure of the bladder and detect if an obstruction is present while the baby urinates. They may also order another type of scan known as renal scintigraphy, which uses a tracer to examine kidney function. Further workup using urodynamic studies can also be done to see how well the bladder stores and empties urine. These tests help determine more definitively if a baby has PUV and its severity.
Based on test results, the healthcare provider can address the urethral/bladder obstruction and prevent any ongoing complications. Regular follow-up care with a urologist (surgical doctor of the urinary tract) and a nephrologist (medical doctor of the kidneys) is crucial to monitor the condition, ensure proper urinary tract functioning and prevent ongoing injury to the kidneys and/or bladder.
Treatment for PUV involves surgical and medical management. The goal is to remove obstruction and prevent complications like chronic kidney disease and bladder damage. If the baby is very sick, they may need breathing assistance. A swollen bladder may also need draining with a catheter. Medications can prevent urinary tract infections and manage symptoms.
Before birth, doctors may consider surgery inside the womb to treat PUV if certain conditions are met. There’s no clear agreement on whether this earlier intervention outweighs the risk to both the pregnant mother and the unborn baby.
After birth, urethral valve ablation is the most common surgical treatment for PUV. The abnormal tissue blocking the urethra is cut using a surgical scope, inserted through the urethra. This surgery is usually performed before the baby leaves the hospital.
Alternative, less common surgeries include making temporary openings in either the bladder (vesicostomy) or the ureter(s) (ureterostomy). Vesicostomy can help when there’s a severe blockage or when a baby is too small for valve ablation. It creates an opening from the bladder to the belly so urine can drain outside the body all the time. This takes pressure off the bladder and kidneys. Vesicostomies are temporary and can be closed later. Ureterostomies are less common but have similar goals. The ureter is disconnected from the bladder and connected to an opening on the belly for drainage. It is also intended to relieve pressure and decrease the risk of infections.
Long-term outcomes for PUV vary greatly depending on the severity of obstruction. Many boys with PUV (~15-40%) will have permanent kidney damage or chronic kidney disease (CKD). Almost all these children will have bladder issues that can be mild or very serious. When children lose kidney function, they can’t make normal urine. They make three to four times more urine than normal each day since the injured kidneys cannot retain it in the body. Children with CKD are then at risk for dehydration if they can’t drink enough fluids.
Regular follow-up care is crucial after treatment to monitor urinary function and prevent complications. This may include check-ups and imaging tests to assess urinary tract functioning. Ongoing medical management may also be necessary to ensure proper urinary function and prevent long-term complications. The treatment team may involve specialties like neonatology, pediatric surgery/urology, nephrology, pediatrics, transplant surgery, psychology, social work and nutrition.
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