Ultrasound Research Today is a free monthly online journal that collates and summarizes the latest research about Ultrasound, including details on screening, diagnosis, pregnancy, detection.

Isolated fetal pyelectasis and chromosomal abnormalities.

Coco C, Jeanty P

Department of Ultrasound, Women's Health Alliance, Nashville, TN, USA. cl.coco@vodafone.it

OBJECTIVE: The primary objective of this study was to determine if isolated pyelectasis is a risk factor for trisomy 21. STUDY DESIGN: Twelve thousand, six hundred and seventy-two unselected singleton fetuses were examined by prenatal ultrasound during the second trimester at a single institution. The sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio of pyelectasis (either isolated or in association with other soft markers/structural anomalies) to detect trisomy 21 were calculated. RESULTS: Pyelectasis (anteroposterior pelvic diameter >/=4 mm) was detected in 2.9% (366/12,672) of the fetuses. Among these, 83.3% (305/366) were isolated, and 16.7% (61/366) were associated with other markers/structural anomalies. The prevalence of trisomy 21 was 0.087% (11/12,672) and, among these fetuses, 2 (18.1%) had pyelectasis, 1 isolated, and 1 associated with other markers/structural anomalies. The presence of isolated pyelectasis had 9.09% sensitivity, 97.6% specificity, 0.33% positive predictive value, and 99.9% negative predictive value to detect fetuses with trisomy 21. The likelihood ratio of trisomy 21 in this group of fetuses was 3.79 (95% CI 0.582-24.616). Among fetuses with pyelectasis and other associated markers/structural anomalies, the sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio for trisomy 21 were 9.09%, 99.5%, 1.64%, 99.9%, and 19.2 (95% CI 2.91-126.44). CONCLUSION: In the absence of other findings, isolated pyelectasis is not a justification for the performance of an amniocentesis.

Published 9 September 2005 in Am J Obstet Gynecol, 193(3): 732-8.
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