Fetal obstructive uropathy in trisomy syndromes.

Fetal obstructive uropathy has seldom been described in trisomy syndromes, and its relationship to these syndromes remains unclear. Five trisomic male fetuses, four with trisomy 18 and one with trisomy 21, were identified out of 110 fetuses evaluated for fetal obstructive uropathy. We performed detailed examination on the urinary tracts of four of these fetuses, three with trisomy 18 and one with trisomy 21, following termination in the second trimester. All four had a markedly distended urinary bladder (megacystis), abdominal wall distension, and a small, poorly developed urethra thoughout its full length. All four also had poor development of the prostate with virtual absence of glandular development, as compared to age-matched controls. Posterior urethral valves were not identified in any case. Three of the fetuses (two with trisomy 18 and one with trisomy 21) had unilateral or bilateral hydroureters, and resulting renal tubulocystic or glomerulocystic change. Review of this database reveals an unexpectedly high frequency of trisomies, particularly trisomy 18, suggesting that the relationship may not be coincidental. Abnormal prostate development may be causally related to fetal obstructive uropathies and may be an under-recognized trait in trisomy syndromes. Karyotypic analysis of all fetuses with obstructive uropathy is important since in utero surgical intervention may be contraindicated in cases of fetal aneuploidy.