the bladder wall may show trabeculations or sacculations or even diverticuli.Diagnosis can also be made by cystoscopy, where a small camera is inserted into the urethra for direct visualization of the posteriorly positioned valve. A limitation of this technique is that posterior valve tissue is translucent and can be pushed against the wall of the urethra by inflowing irrigation fluid, making it difficult to visualize. Cystoscopy may also demonstrate the bladder changes.Centers in Europe and Japan have also had excellent results with cystosonography, although it has not been approved for use in the United States yet. Classification
Posterior urethral obstruction was first classified by H. H. Young in 1919.
The verumontanum, or mountain ridge, is a distinctive landmark in the prostatic urethra, important in the systemic division of posterior valve disorders:Type I - Most common type; due to anterior fusing of the plicae colliculi, mucosal fins extending from the bottom of the verumontanum distally along the prostatic and membranous urethra
Type II - Least common variant; vertical or longitudinal folds between the verumontanum and proximal prostatic urethra and bladder neck
Type III - Less common variant; a disc of tissue distal to verumontanum, also theorized  to be a developmental anomaly of congenital urogenital remnants in the bulbar urethraDewan has suggested that obstruction in the posterior urethra is more appropriately termed congenital obstructions of the posterior urethral membrane (COPUMs), a concept that has come from an in-depth analysis of the historical papers, and evaluation of patients with a prenatal diagnosis that has facilitated video recording of the uninstrumented obstructed urethra. The congenital obstructive lesions in the bulbar urethra, named Type III Valves by Young in 1919, have been eponymously referred to as Cobbs collar or Moormans ring. For each of the COPUM (Posterior Urethra) and Cobbs (Bulbar Urethra) lesions, the degree of obstruction can be variable, consistent with a variable expression of the embryopathy. The now nearly one hundred year old nomenclature of posterior urethral valves was based on limited radiology and primitive endoscopy, thus a change COPUM or Cobbs has been appropriate.