Prenatal sonographic predictors of postnatal pyeloplasty in fetuses with isolated hydronephrosis.

Abstract

To define prenatal sonographic predictors of ureteropelvic junction obstruction requiring postnatal pyeloplasty, in fetuses with isolated hydronephrosis. Retrospective data on prenatal sonographic parameters were compared between patients who had been diagnosed prenatally with hydronephrosis and either underwent postnatal pyeloplasty for ureteropelvic junction obstruction (n = 39) or were treated conservatively (n = 30). Significant differences between the surgically and conservatively treated patients were found for mean anterior-posterior renal diameter (22.8 ± 8.6 vs 14.2 ± 5.9 mm, respectively, p < 0.0001) and parenchymal thickness (5.9 ± 2.8 vs 8.1 ± 2.6 mm, p = 0.009). Anterior-posterior diameter >14 mm was the best single predictor of the need for surgery (area under the ROC curve, 0.817), with sensitivity 77%, specificity 69%, positive predictive value (PPV) 77% and negative predictive value (NPV) 69% (β = 1.17, 95%CI = 1.07-1.28, p < 0.001). Mean ratio of anterior-posterior diameter to parenchymal thickness was significantly higher in the postnatal pyeloplasty group (5.4 ± 4.5 vs 2.1 ± 1.4, p = 0.0001). A ratio >2.1 had a sensitivity of 87% and specificity of 65% for the need for surgery (area under the curve 0.822, PPV 79%, NPV 77%; β = 1.92, 95%CI = 1.16-3.17, p < 0.001). In cases of prenatal isolated hydronephrosis, the pelvic anterior-posterior diameter and parenchymal thickness may predict the need for postnatal pyeloplasty. A ratio of >2.1 of pelvic anterior-posterior diameter to parenchymal thickness suggests ureteropelvic junction obstruction and supports the use of more intensive prenatal and postnatal surveillance.