Posterior urethral valves.

Posterior urethral valves represent the most common post-vesical obstructive malformation. They affect the male gender and appear as intraluminal folds located immediately proximal to the verumontanum. One of the most credited pathogenetic theories considers them an anomalous insertion of mesonephric duct into the cloaca or an incomplete involution of plicae colliculi. At present, the diagnosis of posterior urethral valves is prenatal and the pattern is characterized by detrusor hypertrophy and more or less marked hydroureteronephrosis. Urinary tract disorders that accompany posterior urethral valves include moderate hydroureteronephrosis to severe functional impairment of the entire urinary tract with consequent renal failure. Treatment of posterior urethral valves consists in their resection. At present, with miniaturized endoscopes, valve fulguration is feasible also in newborn infants. In low-weight patients or in case of poor general condition, temporary external urinary bypass (e.g. cystostomy) is feasible.