Third trimester ultrasound better predicts postnatal surgery for hydronephrosis

Abstract

Purpose Surgery for post-natal persistence of clinically significant hydronephrosis is poorly predicted by the anteroposterior diameter of prenatal pyelectasis. We sought to determine if the timing of pyelectasis in either the second or third trimester could better predict the need for surgery. Material and methods A database query for fetal pyelectasis in our maternal-fetal registry for all fetuses with pyelectasis. Utilizing >7mm in 2nd trimester and >10mm in 3rd trimester, patients were then selected for review of post-natal imaging and clinical outcome (Fisher's exact test). Results 59 children with 116 involved kidneys were identified. Second trimester pyelectasis correlated with the degree of post-natal hydronephrosis (Grade 3 or 4; p=0.03), but not the need for surgery (p=0.61). Third trimester pyelectasis also correlated with pos-natal hydronephrosis (p=0.0005), and predicted those requiring surgical intervention (p=0.0001). Eleven children (18%)came to surgery during the 5 year follow-up. Surgery was for progressive obstruction, ectopia, and one child with VUR with recurrent pyelonephritis. Conclusions A third trimester ultrasound for fetal pyelectasis is a better predictor of post-natal outcome than the second trimester.