Fetal hydronephrosis: considerations regarding urological intervention.

Real-time ultrasonic imaging during pregnancy has made it possible to diagnose accurately fetal hydronephrosis as early as at 17 weeks of gestation. The ultrasonic finding of oligohydramnios in conjunction with megacystis and bilateral hydronephrosis is the most reliable indicator of marked permanent urinary tract obstruction and, therefore, is an absolute requirement for fetal urological intervention. Fetal intervention by means of percutaneous catheter drainage of the bladder into the amniotic space is undertaken to preserve renal and pulmonary function. It appears that urinary tract decompression at 17 weeks of gestation is unable to prevent renal dysplasia. The degree to which renal cortical function is preserved by fetal drainage of the hydronephrotic kidney is unknown. Experimental evidence has suggested that early urinary tract decompression promotes improved pulmonary development, which may allow for normal pulmonary function postnatally. We report 6 cases that illustrate important considerations with regard to urological intervention for fetal hydronephrosis.