Background and aims There has been an increase in reporting of antenatal hydronephrosis with increasing use of antenatal sonography. It is known that renal pelvic dilatation (RPD) occurs in 1% of fetuses. This study was aimed to ascertain the postnatal outcome associated with antenatal RPD or other renal abnormality and to recommend a guideline for postnatal management.

Methods We retrospectively analysed data of 50 infants born between August 2011 and July 2013. 49 infants had renal tract abnormality detected on antenatal sonography. Inclusion criteria were presence of renal tract anomaly or isolated RPD ≥7 mm on prenatal sonography, postnatal ultrasound and at least one follow up in designated Consultant clinic. All infants with RPD ≥7 mm were started on prophylactic Trimethoprim.

Results Out of 50 infants, 16 (32%) had normal postnatal scan. 11 (22%) infants had transient/idiopathic hydronephrosis. The second most common diagnosis was Unilateral Pelvi ureteric Junction (PUJ) anomaly found in 9 (18%) infants. Out of these 9 infants, 5 (55.5%) had antenatal RPD ≥15 mm. Only 4 infants were noted to have Vesico Ureteric Reflux (VUR). In total, 11 out of 50 (22%) infants required urological intervention. None of 49 infants have had a culture positive urinary tract infection.

Conclusion These data support that most cases of antenatal RPD, especially isolated unilateral RPD ≤10 mm resolve spontaneously. In contrast, infants with RPD ≥15 mm either unilateral or bilateral had significant uropathy requiring intervention. We also recommend that antibiotic prophylaxis be targeted to high risk infants (RPD ≥10 mm).