Prenatal diagnosis from fetal urine in bladder outlet obstruction: Success rates for traditional cytogenetic evaluation and interphase fluorescence in situ hybridization

Purpose: To determine the optimal approach to the prenatal chromosome analysis of fetal urine from fetuses with bladder outlet obstruction. Methods: Retrospective evaluation of traditional cytogenetic and interphase fluorescence in situ hybridization (FISH) analysis on fetal urine specimens from fetuses with bladder outlet obstruction. Results: Traditional cytogenetic analysis was successful on 71 (95%) of 75 samples, and FISH was informative on 20 (65%) of 31 specimens. The combination of traditional cytogenetic analysis and FISH yielded a 96% diagnostic success rate. The mean turnaround time was 8 days (range 5-14) for traditional cytogenetic analysis and 1.6 days (range 1.0-4.0) for FISH. Chromosome abnormalities were detected in 6 (7.9%) of 76 pregnancies. Conclusion: Traditional cytogenetic analysis achieves a high success rate (95%) and is superior to FISH for chromosome evaluation of fetal urine. However, FISH,,when informative, can complement traditional cytogenetics as it will expeditiously rule out common trisomies in fetuses with bladder outlet obstruction.