Sonographic analysis of the fetus with ureteropelvic junction obstruction.

Twenty-five fetuses with ureteropelvic junction obstruction were evaluated to determine the likelihood of progression of hydronephrosis in utero, and the outcome for the neonate. Such information may alter prenatal as well as perinatal management. These observations showed that the degree of dilatation in utero is likely to be greater than that observed postnatally; the degree of dilatation does not necessarily correlate with renal functional impairment measured postnatally; significant progression of dilatation in utero is relatively uncommon, especially in unilateral cases; and uretero-pelvic junction obstruction, even when bilateral, is unlikely to be fatal. Of 21 live newborn infants with follow-up, 14 required surgery and seven were placed under observation.