Posterior Urethral Valves

Posterior urethral valves are the most common cause of urinary tract obstruction and chronic kidney disease resulting from obstructive uropathy in the pediatric population. The valves are actually obstructing membranous folds situated within the posterior urethral lumen attached to the verumontanum. These folds are found exclusively in male patients. Posterior urethral valves were first described by Morgagni in 1717. Langenbeck further observed valve-like folds in dissected cadavers in 1802, and Hugh Hampton Young reaffirmed their presence in 1919. Posterior urethral valves can lead to a broad range of pathological conditions, spanning from asymptomatic cases to incompatible with sustaining life. Complications may encompass acute and chronic urinary retention, renal failure, bladder outlet obstruction, hydroureteronephrosis, vesicoureteral reflux, voiding dysfunction, and, in severe cases, pulmonary hypoplasia secondary to decreased amniotic fluid levels. Posterior urethral valves are classically split into 3 subtypes based on Young's criteria, which delineate the orientation of the valves within the urethra.  Posterior urethral folds (plicae colliculi) originate from the caudal verumontanum along the lateral margins of the urethra. These folds fuse anteriorly, causing an obstruction. They represent remnants of the Wolffian duct.  Bicuspid leaflets or membranes are attached to the bladder neck proximally, originating from the verumontanum. These are now considered hypertrophic plicae colliculi, not true obstructive posterior urethral valves.  A round membrane situated at the caudal verumontanum, featuring a hole in the middle that is either above the verumontanum (type IIIa) or below (type IIIb). Neither subtype's hole directly communicates with the verumontanum. Nevertheless, this classification has faced challenges. Dewan suggested that types I and III, as Young described, may represent the same structure. They posit that these structures appear distinct only because a central defect ruptures antenatally either naturally or due to iatrogenic instrumentation before birth. In place of the term posterior urethral valves, Dewan introduced the concepts of a congenital obstructive posterior urethral membrane and "Cobb's collar." :  An alternative term for the classic type of posterior urethra valves and is always associated with the verumontanum. This congenital lesion manifests as a potentially obstructive proximal membrane featuring paramedian folds or leaflets extending along the posterior urethral wall to the verumontanum.  Not a valve or a classical posterior urethral valve but a congenital bulbar urethral stricture or obstructive membrane unassociated with the verumontanum. Located distally to the verumontanum in the bulbar urethra, it remains separate from the verumontanum and the external urinary sphincter. This anomaly is believed to represent a persistent remnant of the urogenital membrane.