Posterior Urethral Valves
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A posterior urethral valve (PUV) is an embryologic remnant of tissue in the urethra that causes obstruction of the lower urinary tract during fetal development; this obstruction results in short-and long-term structural abnormalities and physiologic dysfunction in the genitourinary system (kidney, ureter, bladder, and urethra).
- Most common cause of lower urinary tract obstruction in males
- The incidence is estimated to be between 1:3,000 and 1:8,000 live male births.
- Approximately 24–45% of children born with PUV will exhibit renal insufficiency during childhood.
- PUV accounts for up to 17% of the cases of children with end-stage renal failure.
- Majority of cases are isolated and occur sporadically.
- Rarely, cases have been reported in siblings.
- Multiple theories exist as to the embryologic origin of PUV.
- Male urethral development is usually complete by 14 weeks’ gestation; PUV formation is presumed to occur prior to this point.
- Possible embryologic origin of PUVs include (1) presence of an obstructing membrane in the posterior urethra, (2) overgrowth or abnormal folding during normal urethral development, (3) abnormal integration of the Wolffian ducts into urethral development, or (4) abnormal persistence of the urogenital membrane.
- PUVs exist in a spectrum of severity, likely related to the timing and degree of obstruction during development.
- The valve is a leaflet or membrane of thin connective tissue that extends from the anterior urethral lip to the verumontanum posteriorly, obstructing the normal flow of urine through the urethra. This results in an elongated urethra and upstream dilation in the urinary system.
- PUVs are commonly associated with intrinsic renal dysplasia. Studies have demonstrated that dysplastic renal parenchyma at time of birth is permanent.
- Commonly associated pathophysiologic findings in children with PUV include (1) hydroureteronephrosis, (2) dilated bladder with trabeculations and/or diverticulum, and (3) vesicoureteral reflux.
- PUVs may result in early or late bladder dysfunction with decreased compliance and increased voiding pressure that affect both the storage and expulsion of urine as well as expose the upper tract of the urinary system to increased pressure, which leads to worsening renal function over time.
Commonly Associated Conditions
- Genitourinary: hydroureteronephrosis, vesicoureteral reflux, bladder wall thickening and diverticulum, obstructive urinary symptoms, urinary ascites in cases of bladder rupture, perirenal urinoma in cases of renal collecting system rupture
- Varying degrees of renal insufficiency may also be present in patients from birth through adulthood.
- PUV has been associated with other congenital anomalies of the genitourinary tract: prune belly syndrome, imperforate anus, and congenital heart disease.