Aims Renal tract dilatation is commonly detected during antenatal anomaly scanning. This can, however, be a transient phenomenon which resolves on postnatal scanning. There is some debate regarding which babies require postnatal scanning in order to detect significant abnormalities, whilst avoiding over-investigation and unnecessary parental anxiety. Currently all babies with antenatal hydronephrosis (ANHN) born within our trust have a screening ultrasound scan within the first 4 weeks of life. As part of the process of designing a regional protocol for investigation of antenatal renal abnormalities we wanted to determine which risk factors were more predictive of significant postnatal pathology.

Methods We carried out a computer search using the hospital’s radiology IT system in June 2014 to list all babies born between the 1st of March and 31st of August 2013 who had renal imaging carried out. We then looked at the request forms to determine the reason for the request, focussing specifically on babies with ANHN or a family history of vesicoureteric reflux (VUR). We also looked at the results and timing of each investigation performed.

Results 186 patients had renal imaging carried out, 18 of these (9.7%) were scanned due to ANHN and 25 (13.4%) had a family history of VUR only. Of the 18 babies with ANHN, one had PUJ obstruction, four had grades 3–5 VUR, one had poor drainage, one had a duplex kidney and one had a multicystic dysplastic kidney. All patients with significant pathology had a renal pelvis diameter of ≥10 mm on postnatal scans (when recorded). Seven patients had RPD ≥10 mm on the first scan and of these three (42.9%) had significant abnormalities. Of the 25 patients with a family history of VUR two had grade 1 VUR and one had grade 2 VUR.

Conclusions A renal pelvis diameter of greater than or equal to 10mm postnatally is a good predictor of significant renal pathology. A family history of VUR is less predictive of significant renal pathology.