INTRODUCTION: This study aimed to evaluate postnatal outcomes in fetuses with isolated hydronephrosis diagnosed prenatally and to determine factors for progression and the need for surgical intervention based on the Urinary Tract Dilation (UTD) classification system.
METHODS: This retrospective study included fetuses with isolated hydronephrosis diagnosed in the second trimester. Fetal ultrasound data were classified using the UTD system in the second and third trimesters, as well as postnatally. Sonographic parameters (renal pelvis diameter, peripheral calyceal dilatation, parenchymal echogenicity, cortical cysts, and ureteral dilatation) were recorded. Postnatal outcomes, including surgical interventions, were assessed. Comparative analyses were performed between progressing and non-progressing cases, as well as surgical and non-surgical groups.
RESULTS: Of the 133 fetuses diagnosed with isolated prenatal hydronephrosis, 20.3% (n=27) showed progression, 8.3% (n=11) showed regression, and 71.4% (n=95) remained stable between the second and third trimesters. Postnatal surgery was required in 21.8% (n=29) of cases. Higher UTD grades in the second and third trimesters were significantly associated with both progression and the need for surgery (p<0.001). In the second trimester, peripheral calyceal dilatation (p<0.005), increased parenchymal echogenicity (p<0.05), and ureteral dilatation (p<0.01) were more common in the surgical group. In the third trimester and postnatally, renal pelvis diameter, decreased parenchymal thickness, and bilateral abnormalities were significantly higher in the surgery group (p<0.001).
DISCUSSION AND CONCLUSION: While most cases of prenatal hydronephrosis remain stable or regress, 1 in 5 may progress, especially those with higher UTD grades. The UTD classification provides superior prognostic information compared to renal pelvis diameter alone and is valuable in identifying patients at higher risk for postnatal surgery.