The urethral diaphragm, sometimes termed the urethral web or membrane,

is a form fruste of posterior urethral valves or congenital

obstructing urethral membrane.  It represents an unusual persistence

of bands of tissue arising from the fins of the urethral ridge. 

These may join anteriorly to form a "bicuspid valve" rather than

complete membrane.  When the membrane is complete or nearly so,

obstruction may occur and the condition of posterior urethral valves

and its obstructive uropathy follows.   Patients with a urethral

membrane may be completely asymptomatic and most cases are found

incidentally during the work-up a urinary tract infection or

hematuria.  It is possible that a subclinical obstruction may put the

patient at risk for infection, but there is no significant increased

incidence of vesico-ureteric reflux.  If symptoms are persistent, fulgaration can be used to treat the valves.

Krishnan A, De Souza A, Konijeti R, Baskin L, The Anatomy and

Embryology of Posterior Urethral Valves. J Urol. 2006 Apr 175,

12214-1220

Imaji R, Moon DA, Dewan PA Congenital posterior urethral membrane:

variable morphological expression J Urol. 2001 Apr; 165(4):1240-2

Posterior urethral valves

Cobb’s collar

Plicae colliculi