Third trimester ultrasound of fetal pyelectasis: Predictor for postnatal surgery ☆

Abstract Objective The ability to predict surgically relevant fetal renal pyelectasis is limited. We sought to determine whether the intrauterine timing of prenatal pyelectasis can predict the need for postnatal surgery. Methods We retrospectively reviewed all patients with ultrasound measurements of the fetal renal pelvis during the 2nd and 3rd trimesters and postnatally. Pyelectasis was defined as >7 mm for renal pelvis antero-posterior diameter in the 2nd trimester and >10 mm in the 3rd trimester. Results Fifty-nine patients out of 2397 candidates met the criteria for inclusion. A total of 116 kidneys were analyzed independently. Second trimester pyelectasis was associated with grade of postnatal hydronephrosis but not the need for surgery. Third trimester pyelectasis was associated with both postnatal hydronephrosis and surgery. The positive and negative predictive values for postnatal surgery were respectively 18% and 95% in the second trimester, and 27% and 100% in the third trimester. Conclusions Third trimester ultrasound for fetal pyelectasis was better able to predict surgically relevant hydronephrosis than second trimester ultrasound.