Ultrasound screening for congenital pyelectasis in term pregnancies.

The purpose of this study was to compare the role of antenatal ultrasound screening for congenital pyelectasis at term with postnatal screening. An ultrasonographic prospective study of 231 fetuses of low-risk pregnancies was performed, evaluating the renal pelvis at term (38 to 42 weeks gestation) and after birth (first and third months of life). Cut-off points used were 9 mm antenatally, and 10 and 12 mm, respectively postnatally, all in an anteroposterior view. A sensitivity of 20% and a specificity of 93.4% was obtained when comparing the antenatal versus the third-month scan, whereas when we compared the sonograms from the first versus the third month of life, we found a sensitivity of 60% and a specificity of 89.7%, with a positive predictive value of 14.7% in the first case and 25% in the second case. A p value < 0.001 was obtained when comparing the sensitivities; a p value of 0.2 was reported when comparing the specificities. Data on a comparative screening of the renal pelvis measured antenatally at term and postnatally do not exist. Although it is extremely feasible, the measurement of the fetal renal pelvis during the routine ultrasound scan at term of gestation seems of no benefit in terms of sensitivity and positive predictive values in identifying infants affected by congenital pyelectasis. Because of the low values of sensitivity obtained in our study, a screening program for the renal pelvis dilation both in fetuses and newborns cannot be recommended.