Ultrasound Markers in Fetal Hydronephrosis to Predict Postnatal Surgery

Parents confronted with the finding of antenatal hydronephrosis (ANH) are particularly interested in whether their baby will need postnatal surgery. The objective of this study was to predict ANH requiring surgery on the basis of the fetal anteroposterior renal pelvic diameter (APRPD) and the Society for Fetal Urology (SFU) grading system.

The medical records of 179 patients with the finding of ANH were reviewed retrospectively. ANH was graded according to the SFU grading system. Prenatal ultrasound examinations were correlated to postnatal outcome, which was divided into three groups: prenatal resolution, conservative management and surgical treatment.

58 (32.4 %) cases were classified as prenatal resolution, 89 (49.7 %) babies were assigned to the conservative outcome group and 32 (17.9 %) patients needed surgical repair. Postnatal surgery was best predicted in the second trimester (area under the receiver operating characteristics curve: 0.839) by an APRPD cut-off of 8.3 mm (sensitivity: 77.8 %; specificity: 85.7 %; PPV of 53.9 %, NPV of 94.7 %). The combination of the parameters "progression of SFU grade" and SFU grade 3 or 4 achieved a sensitivity of 84.4 % and a specificity of 80.3 % for the prediction of surgery.

Second-trimester APRPD is a useful parameter for predicting the risk for postnatal surgery. The SFU grade should be assessed in every prenatal ultrasound examination as some further risk estimates can be made based on its dynamics over time.