EP06.14: Natural history and postnatal outcome of obstructive uropathies/hydronephrosis confirmed in the third trimester of pregnancy

This study aimed to elucidate postnatal diagnosis and outcomes of fetuses with antenatal suspicion of obstructive uropathies and/or hydronephrosis persisting into the third trimester of pregnancy. This retrospective study was conducted between 2013-2023 and included 213 fetuses with ultrasound suspicion of hydronephrosis (anteroposterior renal pelvic diameter ≥10 mm) and/or obstructive uropathies persisting during the third trimester of pregnancy. Follow-up of the cases focused on the final postnatal diagnosis and the need for surgical intervention, including nephrectomy. Among the 213 fetuses with a prenatal suspicion, 65% were postnatally diagnosed with upper urinary tract obstruction (UUTO), 12% with lower urinary tract obstruction (LUTO), 11% with a pathologic duplex system, 3% with isolated vesicoureteral reflux (VUR), 4% with multicystic kidney disease (MCKD) and only 5% exhibited a normal urinary tract without hydronephrosis postnatally. Interestingly, the coexistence of two diagnoses was observed in 6% of these cases, most frequently the combination of lower and upper urinary tract obstructions (3%). The overall survival rate was 98%, with all neonatal deaths occurring within the LUTO group. An afunctional kidney was observed in: 100% of the MCKD cases, 57% of infants with isolated VUR, 27% of the LUTO cases and 12.5% of cases with a pathologic duplex system. Surgical intervention was deemed necessary in 100% of LUTO cases, 86% of infants with VUR, 43% of UUTO cases and 13% of infants with MCKD. This study highlights the strong correlation between third trimester diagnosis of urinary tract hydronephrosis/obstructive uropathies and postnatal findings with extremely low false-positive rates. These conditions are characterised by high survival rates, but significant morbidity, with high rates of single non-functional kidney and need for surgical intervention, particularly in cases of LUTO, VUR and a pathologic duplex system.