The posterior urethral valve is a malformation characterized by an obstructive membrane in the urethra affecting urinary flow, which can cause kidney failure.
Posterior urethral valve (PUV) is a rare condition that affects the male urinary tract. This condition is characterized by an obstructive membrane that is located at the back of the urethra near the bladder, between the prostate and the external urethral sphincter.
According to urologist Dr. Ubirajara Barroso Jr., head of the Urinary System Unit at the Professor Edgard Santos University Hospital (UFBA), the incidence of posterior urethral valve is on average 1 in every 8,000 live births.
Posterior urethral valve is a condition that requires detailed understanding, early diagnosis and appropriate treatment to avoid serious complications.
In this guide, we'll cover what it is, what the possible causes are, characteristic symptoms and the treatment options available for the posterior urethral valve. Read on and check it out.
What is the posterior urethral valve?
The posterior urethral valve is a congenital anomaly in the structure of the male urethra. It involves an abnormal membrane inside the urethra, which can partially or completely obstruct urine flow. This obstruction can lead to serious complications if not treated properly.
"In fact, what exists is not a real valve, but a membrane, but as this nomenclature, given at the beginning of the last century, has been used by time, it remains today," explains Dr. Ubirajara Barroso, who is also head of the division of reconstructive urological surgery and pediatric urology at the Federal University of Bahia Hospital.
He explains that the posterior urethral valve can be type 1, type 2 or type 3.
Type 1 posterior urethral valve:
Type 1 is the most common, accounting for approximately 95% of cases. This condition involves the presence of a membrane that forms an open arch in the lower portion of the urethra.
"Some theorize that type 1 would actually be more open due to the urethral sounding in which all the valves are somehow concentric," he explains.
Type 2 posterior urethral valve:
Type 2 is characterized by a fold in the mucosa. According to Dr. Barroso, some experts believe that it is not actually a valve.
Type 3 posterior urethral valve:
Type 3 is similar to an orifice, being a concentric membrane, and is considered the most problematic, as it can cause significant complications in the bladder.
"The posterior urethral valve causes significant damage to the bladder because the bladder muscle, which is the detrusor muscle, needs to contract with increasing force in order to expel urine. This causes muscle hypertrophy and the deposition of collagen, fibrosis and increased pressure inside the bladder," describes Dr. Barroso, who points out that these contractions can cause irreversible damage to the kidneys, i.e. renal failure.
What are the causes of a posterior urethral valve?
The exact cause of the posterior urethral valve is still not fully understood, but it is believed that genetic factors and abnormalities in the development of the urethra during pregnancy are involved.
"It is estimated that there is some genetic issue involved, but as it is in the posterior urethra, in a region where the prostate exits in a structure called the verumontanum, it is believed that the origin of the problem lies in the formation of this portion with a persistent membrane or in the insertion of the verumontanum in the urethra," says the doctor who also works in pediatric and reconstructive urology in São Paulo.
Diagnosis and symptoms of posterior urethral valve
According to Dr. Barroso, most posterior urethral valves are currently identified during the prenatal period.
Detection is carried out when there is:
- Presence of bilateral renal dilatation;
- Ureteral dilation;
- A distended bladder that is unable to empty properly, with thick walls.
Later, after the child is born or is older, the posterior urethral valve can be diagnosed:
- Urinary infection, usually with fever;
- Difficulty urinating;
- It takes a while for the jet to start;
- Weak jet;
- Urinary urgency;
- Incontinence urinary.
Diagnosis is usually made using voiding cystourethrography, a test in which a probe is passed through the urethra and iodine is injected. The contrast allows the urethra to be visualized during urination and the presence of the obstructive membrane to be identified.
"The child has to be in an oblique or lateral position to better assess the entire urethral anatomy in search of the presence of this obstructive membrane," he explains.
Treatment and new approaches for the posterior urethral valve
Dr. Ubirajara Barroso points out that the posterior urethral valve is treated by endoscopy with visualization of the valve, where an ablation is performed.
"For those children with kidney failure, it is sometimes necessary to perform a urinary shunt, which is a temporary detour of transit to the skin, which can be from the bladder to the skin, called a vesicostomy, or from the ureter to the skin, called a cutaneous ureterostomy," he says.
According to Dr. Ubirajara Barroso Jr., new approaches are being explored to offer more precise and effective treatments. "A novelty in treatment is bladder catheterization at night, the child with a urethral valve has an open night catheterization, this was Stephen Koff's idea," he says.
This method involves open nocturnal catheterization in children with a urethral valve, taking advantage of the period when they tend to have polyuria (excessive urine production and elimination), ensuring that the bladder remains at low pressure for 8 to 10 hours during sleep. This practice has been shown to be effective in reducing the incidence of kidney failure, providing relief to bladders suffering from valve obstruction.
Another important innovation is laser treatment of the posterior urethral valve. "The advantages of this type of treatment are not yet well documented, but technically it is possible to ablate the valve with greater precision and probably reduce the risk of sphincter injury," he points out.
In addition, the importance of urodynamic studies after valve ablation has been established. This procedure is essential for assessing bladder function and initiating early treatment of possible dysfunctions, either through the use of anticholinergics or alpha-blockers.
Post-treatment care and follow-up
Dr. Barroso emphasizes that even after treatment of the valve, urodynamic studies show that 75% of people after ablation have involuntary bladder contractions, which causes the bladder to continue to be affected by urinary effort, resulting in persistent changes.
"This can lead to symptoms of urinary urgency, the risk of urinary incontinence and the need for containment maneuvers to prevent this loss," he says.
The specialist says that in these cases, even if the valve is treated early, the lack of subsequent bladder treatment can result in late complications, including kidney failure.
In addition, after valve treatment, due to the effects it has on the kidneys, there is a change in the urinary concentration of electrolytes, resulting in an increase in urine production during the day, which is called polyuria.
"Polyuria can further increase bladder overload and the risk of permanent bladder dysfunction," he warns.
It is extremely important that children who have undergone valve ablation receive follow-up care from a urologist, especially after the period of weaning, in order to prevent these changes in the long term and ensure an adequate quality of life.
Do you notice any of the symptoms described in this text in your child? Has he already undergone treatment for a posterior urethral valve? If so, it's important to schedule a doctor's appointment for a proper evaluation and to ensure that he receives the necessary follow-up for his urinary health.
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