First Trimester Fetal Renal Pelvis Diameter Cut-Off Values for Predicting Fetal Pelviectasis in Advanced Gestation

We aimed to evaluate whether first-trimester fetal renal pelvis anteroposterior diameter measurements are associated with second- and third-trimester fetal pelviectasis and to describe postnatal surgical outcomes.

Fetal renal pelvis anteroposterior diameter measurements between 11 and 14 weeks of gestation, 20 and 24 weeks of gestation, and above 32 weeks of gestation were evaluated retrospectively in 122 patients who were followed up in our perinatology outpatient clinic. Fetuses with pelviectasis were identified at later gestational weeks. Postnatal outcomes were followed, and the need for surgery was questioned in third trimester fetuses with values above 7 mm. The diagnostic value of fetal renal pelvis anteroposterior diameter at 11-14 weeks of gestation was investigated to determine fetal pelviectasis in advanced gestation and postnatal outcomes.

Fetal renal pelvis anteroposterior diameter values above 2 mm predicted second and third trimester fetal renal pelviectasis with a sensitivity of 42.1%, specificity of 85.4%. Postnatal surgical intervention was required in four fetuses. Two fetuses with third trimester RPAPD values of 9 mm underwent stent implantation, one fetus with an RPAPD of 19 mm underwent right partial upper pole nephrectomy, and one fetus with an RPAPD of 15 mm underwent stent implantation twice. Because of the very small number of surgical events and the heterogeneity of the procedures, this outcome was evaluated descriptively.

First trimester fetal renal pelvis anteroposterior diameter measurement appears feasible during routine ultrasound examination and shows a significant but limited association with pelviectasis in later gestation. Although the > 2 mm threshold demonstrated relatively low sensitivity, its acceptable specificity suggests that this parameter may provide preliminary evidence for future studies evaluating early fetal urinary tract assessment. However, no definitive conclusion can be drawn regarding postnatal surgery because of the very small number of surgical events.