 Posterior Urethral Valves (PUV)
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Posterior urethral valves(PUV), a congential condition that occurs only in boys, are excess flaps of tissue in the urethra, which is the tube that drains urine from the bladder to the outside of the body for elimination. See Urinary Tract Anatomy. This excess tissue can block or reverse the flow of urine and can affect all of the urinary tract organs including the urethra, bladder, ureters, and kidneys. The organs of the urinary tract become engorged with urine and swell, causing tissue and cell damage. The degree of urinary outflow obstruction will determine the severity of the urinary tract problems.
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PUV are the most common cause of severe types of urinary tract obstruction in boys. It is thought to develop in the early stages of fetal development. The abnormality affects only male infants and occurs in about one in 8,000 births. Sometimes however, if it isn't severe, it is not detected during infancy. This disorder is usually sporadic (occurs by chance). However, some cases have been seen in twins and siblings, suggesting a possible genetic component.
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The syndrome may occur in varying degrees from mild to severe. The following are the most common symptoms of posterior urethral valves. However, each child may experience symptoms differently. Symptoms may include:
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- an enlarged bladder that may be detectable through the abdomen as a large mass
- urinary tract infection, or UTI (usually uncommon in children younger than 5 years and unlikely in boys at any age, unless an obstruction is present)
- painful urination
- weak urine stream
- urinary frequency
- bedwetting or wetting pants after the child has been toilet-trained
- poor weight gain
- difficulty with urination
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The symptoms of PUV may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.
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The severity of the condition usually dictates when it is identified. In more severe cases, where blockage of urine is complete or almost complete, posterior urethral valves can be identified prenatally in the male fetus. Here, ultrasound findings include bladder distention, bilateral kidney and ureteral dilation, and sometimes, decreased amniotic fluid level (oligohydramnios). It can also be diagnosed in the newborn boy with a distended bladder, and urinary dribbling or urinary retention [Respiratory distress (breathing difficulties) may be present in those with severe obstruction.].
If the blockage was mild at birth, posterior urethral valves can have a gradual effect on the bladder and therefore go undetected for years until your older child has a urinary tract infection or has problems urinating. These problems include the symptoms noted above.
If your child has these symptoms, he should be referred to a pediatric urologic physician immediately for an ultrasound of the urinary tract. The diagnosis is made based on the characteristic appearance of the posterior urethra on an x-ray called a voiding cystourethrogram(VCUG) or by direct endoscopic visualization. A VCUG is a specific x-ray that examines the urinary tract. For this test, a catheter (hollow tube) is placed in the urethra (tube that drains urine from the bladder to the outside of the body) and the bladder is filled with a liquid dye. X-ray images will be taken as the bladder fills and empties. The images will show if there is any reverse flow of urine into the ureters and kidneys. Direct endoscopic visualization is a procedure whereby a miniature telescope is passed within the urethra during general anesthesia. VCUG may also show vesicoureteral reflux (backward flow of urine from the bladder to the ureter and/or kidney), which is present in approximately 50% of patients with posterior urethral valves at the time of diagnosis. Reflux often resolves spontaneously after correction of the obstruction (i.e. treatment of PUV)
Further evaluation is necessary to complete the work up of the patient with posterior urethral valves. Your child will likely undergo laboratory (blood and urine) testing, especially a baseline serum creatinine level, which provides a gross estimation of kidney function. This is essential for the initial evaluation and follow up care of boys with posterior urethral valves. Additional studies you and your child may encounter include; the intravenous pyelogram (IVP) which allows doctors to visualize and assess the kidney collecting system and ureteral (drainage system) anatomy. This test involves injection of a contrast agent that fills the urinary tract tract and helps the doctor to see the organs on an x-ray. A renal (kidney) scan(s) which provide very sensitive quantitative information regarding kidney function and drainage characteristics, may also be used.
Specific evaluation of bladder function (urodynamics) is also an important adjunct to the care of boys with posterior urethral valves. During urodynamic evaluation, the bladder storage and emptying functions are characterized. This allows for appropriate and optimal medical and, at times, surgical management of problems that can be associated with posterial urethral valves. These include: small bladder capacity, hyperactivity of the bladder muscle, stiffness (loss of compliance) of the bladder wall, and/or an inability of the bladder to contract or empty completely (atonic bladder).
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How the doctor manages your child's posterior urethral valves depends on the severity and character of presenting symptoms. In severe cases, for instance, symptoms such as respiratory distress, sepsis and/or fluid and electrolyte abnormalities are treated emergently. A urethral catheter is placed for relief of urinary obstruction, most likely prior to definitive diagnosis in the severely ill newborn, or following a diagnostic VCUG in the patient with less severe symptoms.
After appropriate stabilization of the patient, the posterior urethral valves are either cut or resected during a minimally invasive procedure known as valve ablation. While the child is under general anesthesia, doctors use a small caliber endoscope, a tiny telescope about the size of a pen-filler, to look through the urethra and remove the valves. No incision is necessary. Rarely, a boy with severe manifestations of posterior urethral valves may require initial proximal urinary diversion (urinary drainage before the urine reaches the urethra) at the level of either the bladder, ureter(s) or kidney(s).
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Postoperative and long-term evaluation of patients with posterior urethral valves is mandatory. After stabilization of the patient in the immediate postoperative period, the doctor must consider and manage any long-term problems that posterior urethral valves may have caused or impacted before their removal. These problems potentially include vesicoureteral reflux, bladder dysfunction and/or renal function impairment.
Baseline and periodic (as needed) urodynamic study in all patients with posterior urethral valves is prudent. Appropriate therapy such as anticholinergic medication (to decrease bladder hyperactivity), clean intermittent catheterization (to empty an atonic bladder) and/or bladder augmentation (to increase bladder capacity) may be helpful for management of specific bladder dysfunction.
Manifestations and consequences of posterior urethral valves may persist after removal of the valves. At one end of the spectrum are boys who continue to experience mild symptoms of urinary incontinence, frequency, urgency, but a normal upper urinary tract (kidney and ureter). Simple valve ablation as an outpatient can often cure these symptoms. In severely affected urinary tracts with a dilated kidney(s) and/or ureter(s) which do not improve after valve ablation, extensive reconstructive surgery may be helpful in preventing renal deterioration. Unfortunately, in some cases where the impact on renal function was greatly compromised by the obstruction, chronic renal insufficiency or renal failure occurs despite early relief of the obstruction. Follow-up care is therefore of the utmost importance.
Comprehensive initial and prospective evaluation, coupled with appropriate, directed management and aggressive follow up of boys with posterior urethral valves is critically important for optimal outcome. The goal would be to identify initially, treat proactively, and evaluate systematically the response of specific upper and/or lower urinary tract abnormality(ies) due to posterior urethral valves. This approach potentially limits the harmful effects on bladder and renal function. This goal will best be accomplished by collaboration with specialists in nephrology and radiology.
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Research is being conducted at Children's Hospital Boston to determine the effects of prophylactic medication for these bladders to reduce or prevent their stiffness. Other drug therapies are being investigated that alter the potential changes at the cellular molecular level that may occur in boys with posterior urethral valves.
Researchers are also looking into ways to apply tissue engineering techniques to treat children with posterior urethral valves, who may require reconstructive surgery of the urinary tract. Tissue engineering allows doctors to use the patient's own cells to grow new replacement tissue used to augment various parts of the urinary tract. For more information, link to Children's Hospital's Center for Genitourinary Tissue Engineering.
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