Outcome of prenatally detected bilateral higher urinary tract obstruction or megacystis: sex-related study on a series of 709 cases.

Objective: To compare the sex specific outcome of fetuses with prenatally detected urinary tract dilatation, with the exclusion of pyelectasia.

Method: Included in the study were 709 cases of major dilatation of the fetal urinary tract, diagnosed at routine ultrasound scan. For each sex group, cases were divided into two subgroups depending on the level of dilatation. Final diagnosis was based on postnatal evaluation or on fetal autopsy. Postnatal renal function was evaluated using serum creatinine at two years of age.

Results: Bilateral higher urinary tract dilatation was prenatally observed in 148 (20.8%) and lower urinary tract obstruction or bladder dilatation in 561 (79.1%) of the 709 cases (121 female and 588 male fetuses) (P <0.001). Bladder dilatation was less frequent in female fetuses (62%) than in males (82.6%) (P <0.001). At final diagnosis, associated malformations were observed in 53.7% of female fetuses versus 11% in males (P <0.001). The survival rate was 42.7%. Postnatal renal function, evaluated in 289/303 live infants, was impaired in 29.7% of cases and depended on the level of obstruction, but not on the sex.

Conclusion: Prenatally detected urinary tract dilatation has a poor prognosis both in male and female fetuses. Associated malformations are observed more frequently in female than in male fetuses.