Third trimester ultrasound of fetal pyelectasis: predictor for postnatal surgery.

OBJECTIVE

The ability to predict surgically relevant fetal renal pyelectasis is limited. We sought to determine whether the intrauterine timing of prenatal pyelectasis can predict the need for postnatal surgery.

METHODS

We retrospectively reviewed all patients with ultrasound measurements of the fetal renal pelvis during the 2nd and 3rd trimesters and postnatally. Pyelectasis was defined as >7mm for renal pelvis antero-posterior diameter in the 2nd trimester and >10mm in the 3rd trimester.

RESULTS

Fifty-nine patients out of 2397 candidates met the criteria for inclusion. A total of 116 kidneys were analyzed independently. Second trimester pyelectasis was associated with grade of postnatal hydronephrosis but not the need for surgery. Third trimester pyelectasis was associated with both postnatal hydronephrosis and surgery. The positive and negative predictive values for postnatal surgery were respectively 18% and 95% in the second trimester, and 27% and 100% in the third trimester.

CONCLUSIONS

Third trimester ultrasound for fetal pyelectasis was better able to predict surgically relevant hydronephrosis than second trimester ultrasound.