[Urination disorders revealing posterior urethral valve: radiological aspects].

Posterior urethral valves represent the most common form of congenital urethral obstruction; they are due to the presence of membranous recesses within the posterior urethra. Their consequences on the lower and upper urinary tract depend on the importance of the obstacle. Moderate forms have a late clinical onset in children who present with voiding disorders and a normal upper urinary tract; in such cases, the diagnosis is difficult since typical features are absent on the urethrocystogram. Radiological signs of urethral valves should be differentiated from congenital urethral strictures which are not obstructive and from bladder dysfunctions which modify both the bladder and the urethra during micturition.