Spontaneous resolution of prenatal megalourethra.

Urethral obstruction in the fetus is rare. Whereas proximal obstruction most often is caused by posterior urethral valves, causes of distal obstruction are less well recognized and can include urethral atresia, urethral webs, and anterior urethral valves. These latter abnormalities can lead to urinary retention, incontinence, enuresis, spontaneous bladder rupture, and megacystis. The authors present 3 fetuses (gestational age range, 18 to 20 weeks) in whom distal urethral obstruction was suspected by prenatal ultrasonography in the absence of a demonstrable lesion. All 3 experienced spontaneous resolution of the presumed obstruction. On follow-up, all are alive and well with no adverse genitourinary tract sequelae. No postpartum intervention was required.