673 The Role of the First Postnatal Ultrasound Scan to Predict Outcome in Children with Antenatally Diagnosed Hydronephrosis

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Abstract Aim We aimed to determine if the renal pelvic diameter on the first postnatal scan can predict the need for surgical intervention in children with antenatally diagnosed hydronephrosis. Method Data of all babies with antenatal hydronephrosis born in our centre from 2009–2015 were obtained from the National Congenital Anomaly and Rare Disease Registration Service (NCARDRS). The medical records were analysed retrospectively for diagnosis, investigations, and interventions. Mean follow-up was 7 (4–10) years. The results were expressed as mean and percentage. Statistical data analysis was performed on GraphPad. Results 224 babies were included in the study. 162 (72%) were males, and 92 (39%) had bilateral hydronephrosis. 163 (73%) had spontaneous resolution of hydronephrosis. The resolution rates were similar for unilateral and bilateral cases. The mean renal pelvic diameter was 6.2mm in the resolved group and 16.2mm in the persistent group (p<0.01). The highest renal pelvic diameter undergoing spontaneous resolution was 24mm. Of the 61 (27%) children with persistent hydronephrosis, 38 (17%) children required surgery. Pyeloplasty for pelviureteric junction obstruction was the most common procedure. 23 (10%) patients continued to have persistent dilatation but needed no intervention. Renal duplex was the most common diagnosis in this group, followed by vesicoureteric reflux. All babies with a pelvic diameter of 25mm or above on their first postnatal ultrasound required surgical intervention. Conclusion The majority of antenatal hydronephrosis resolves spontaneously. However, interventions are necessary if the pelvic diameter is above 25mm.