Antenatal staging of congenital lower urinary tract obstruction

AIM: to propose a staging system for congenital Lower Urinary Tract Obstructions (LUTO) capable of predicting the severity of the condition and its prognosis.

METHODS: This was a national retrospective study carried out at the eight Academic Hospitals in the Netherlands. We collected prenatal and postnatal data of fetuses at high-risk of isolated LUTO and managed conservatively. Postnatal renal function was assessed by the estimated glomerular filtration rate (eGFR), calculated with the Schwartz formula, considering the length of the infant and the creatinine nadir in the first year of age. Receiver operating characteristic (ROC) curve, univariate analysis and multivariate logistic regression analysis with stepwise backward elimination were performed in order to identify the best antenatal predictors of perinatal mortality and postnatal renal function.

RESULTS: In total 261 fetuses suspected for LUTO and managed conservatively were included in the study. The pregnancy was terminated in 110 cases and perinatal death occurred in 35 cases. GA at the appearance of oligohydramnios showed an excellent accuracy in predicting the risk of perinatal mortality with an area under the curve of 0.95 (p < 0.001) and an optimal cut-off at 26 weeks' gestation. Fetuses with still normal AF at 26 weeks' gestation presented with low risk of poor outcome and were therefore defined as cases with mild LUTO. In fetuses referred before the 26th week of gestation, the urinary bladder volume (BV) was the best unique predictor of perinatal mortality. ROC analysis identified a BV of 5.4 cm3 at 20 weeks as the best threshold for predicting an adverse outcome. Therefore, LUTO cases with a BV ≥ 5.4 cm3 or abnormal AF before 20 weeks' gestation were defined as severe and those with BV < 5.4 cm3 and still normal AF at the 20 weeks' scan were defined as moderate. Risk of perinatal mortality significantly increased according to the stage of severity from mild to moderate and severe stage, from 8%, to 26% and to 55%, respectively. Similarly, risk of severely impaired renal function increased from 11%, to 31% and to 44%, respectively.

CONCLUSIONS: Gestational age at first appearance of oligo- or anhydramnios and bladder volume at diagnosis can accurately predict mortality and morbidity in fetuses with LUTO. This article is protected by copyright. All rights reserved.