Sonography of fetal micturition.

OBJECTIVE To describe the sonographic visualization of fetal micturition and its role in the diagnosis of posterior urethral valves and hypospadias. METHODS This was a prospective study of 25 male fetuses (21 with bilateral pyelectasis, one whose bladder was being studied because of ureterocele and three with hypospadias), and five female fetuses (with bilateral pyelectasis). A midline sagittal scan of the fetal pelvis, perineum and external genitalia was obtained and observed continuously during fetal micturition. RESULTS In 19 of the 21 male fetuses and the five female fetuses with bilateral pyelectasis micturition was normal, with visualization of urinary bladder contraction, slight fluid distention of the urethra and a urinary stream from the external urethral meatus. In three male fetuses, two with bilateral pyelectasis and the one with ureterocele, the posterior urethra was normal at rest and it ballooned out during micturition, diagnostic of posterior urethral valves. In the three male fetuses with hypospadias the ventral jet of the urinary stream was visualized. CONCLUSION Fetal micturition can be visualized on sonography. It may be of value in the diagnosis of posterior urethral valves and hypospadias.