Diagnostic accuracy of postnatal renal pelvic diameter as a predictor of uropathy: a prospective study

There is a necessity to standardize postnatal ultrasonographic markers predictive of significant uropathies. The purpose of this study was to assess the accuracy of anteroposterior renal pelvic diameter (APD) on postnatal ultrasound to discriminate between significant uropathy and idiopathic renal pelvic dilatation.

Neonates ( n=110) who were found to have isolated fetal renal pelvic dilatation underwent systematic investigation and were prospectively followed up. A US scan was performed after the 1st week of life, and all infants underwent voiding cystourethrography. Neonates with an APD larger than 10 mm were examined with renal scintigraphy. Receiver-operating characteristic (ROC) plots were constructed to determine the best cutoffs for APD to identify renal units with significant uropathy as well as those requiring surgical intervention.

The area under the curve (AUC) estimated by the ROC curve was 0.921 (95% CI=0.869-0.957), indicating excellent discriminant power between nonsignificant pelvis dilatation and significant uropathy. A cutoff of 10 mm for APD showed the best accuracy for identifying infants with a significant uropathy (sensitivity, 90.4%; specificity, 91%). To identify infants who required surgical intervention, the calculated AUC was 0.976 (95% CI=0.940-0.993). A cutoff of 15 mm showed the best diagnostic performance for identifying the renal units requiring pyeloplasty (sensitivity, 100%; specificity, 92.5%).

Our results suggest that postnatal APD is an excellent test for identifying fetuses with significant uropathy, as well as those requiring postnatal intervention.