Frequency and prediction of persistent urinary tract dilation in the third trimester and postnatal urinary tract dilation in the infant following diagnosis in the second trimester.

OBJECTIVE To determine the frequency, associated characteristics, and predictive value of current risk stratification of persistent prenatal urinary tract dilation (UTD) in the third trimester and subsequent postnatal UTD in the infant, following diagnosis in the second trimester using the 2014 UTD consensus classification system. METHODS We conducted a single institution retrospective cohort study of singleton pregnancies diagnosed with unilateral or bilateral UTD in the second trimester (<28 weeks) with follow-up in the third trimester (≥28 weeks) between 2017 to 2019. The primary outcomes included persistent prenatal UTD in the third trimester and postnatal UTD in the infant through 6 months of age. In multivariable analysis, we assessed whether patient and diagnostic characteristics (laterality, non-pelvic dilation and abnormalities [ureter, bladder, parenchymal and/or calyces], degree of pelvic dilation [in millimeters]) affected study outcomes. We assessed the predictive value of current risk stratification (grade A1 vs. A2-3) in the second and third trimester by the area under the receiver operating characteristic curve (AUC). RESULTS Of 26,620 with second trimester ultrasound assessments, 347 patients (1%) had prenatal UTD diagnosed in the second trimester, of which 43% (150/347, 95% CI: 38 to 49%) had persistent UTD in the third trimester. Among 81% (282/347) with postnatal follow-up, the frequency of postnatal UTD was 17% (49/282, 95% CI: 13% to 22%), and among the subset with persistent prenatal UTD, the frequency of postnatal UTD was 45% (46/102, 95% CI: 35% to 55%). The most frequent postnatal diagnosis was transient UTD (76%), followed by duplicated collecting system (10%). Of infants originally diagnosed with UTD, 2% required surgery, or among the 49 infants with postnatal UTD, 14% required surgery. At second trimester diagnosis and also at third trimester follow-up, predictors of both persistent prenatal and postnatal UTD included presence of non-pelvic dilation, larger mean pelvic measurement, and higher grade A2-3. Second trimester grade A2-3 UTD had satisfactory discrimination for predicting persistent prenatal UTD (AUC: 0.64; 95%CI: 0.58 to 0.70) and postnatal UTD (AUC: 0.72; 95%CI: 0.63 to 0.81), as did third trimester grade A2-3 UTD for postnatal UTD (AUC: 0.66; 95%CI: 0.56 to 0.76). CONCLUSIONS Most cases of prenatal UTD did not result in postnatal UTD, few of which required surgery. Repeat third trimester assessment after a second trimester diagnosis is warranted. Current risk stratification by grade using the 2014 UTD consensus classification can be used to predict postnatal UTD. Further research is needed to determine whether predictive performance can be improved with additional risk factors. This article is protected by copyright. All rights reserved.