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Posterior urethral valves are one of the most common causes of urinary tract obstruction in the pediatric population. They are obstructing membranous folds in the lumen of the posterior part of the urethra and are exclusive to male patients. Posterior urethral valves were first described by Morgagni in 1717 and then by Langenbeck in 1802, who reported valve-like folds in dissected cadavers. Posterior urethral valves can lead to a spectrum of pathology both inside and outside the urinary system. This includes acute retention, chronic kidney disease, and in severe cases, pulmonary hypoplasia secondary to low amniotic fluid levels.

Posterior urethral valves are classically split into three subtypes by Young's criteria according to the orientation of the valves within the urethra.

  1. Type I: 95% - Posterior urethral folds (Plicae colliculi), which arise from the caudal verumontanum along the lateral margins of the urethra fuse anteriorly causing an obstruction.

  2. Type II: Membranes cranially attached to the bladder neck originating from the verumontanum. These are now thought to be due to hypertrophy of the plicae colliculi and not obstructive valves.

  3. Type III: 5% - Round membrane at the caudal verumontanum with a hole in the middle that is either above (type IIIa) the verumontanum or below it (type IIIb). Neither subtype's hole communicates directly with the verumontanum.

However, this classification has been challenged. Dewan suggested that types I and III described by Young are the same structure that only appears to be distinct entities following a central defect rupturing antenatally naturally or due to iatrogenic instrumentation. In a subsequent paper, they replaced the term posterior urethral valves with a congenital obstructive posterior urethral membrane (COPUM) and Cobbs collar. The latter is not a valve but a congenital stricture and distinct from COPUM in that it is not associated with the verumontanum.

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Last updated; Jan. 2021

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