Outcome and management of isolated moderate renal pelvis dilatation detected at postnatal screening

The aim of this study was to evaluate the incidence and outcome of isolated moderate renal pelvis dilatation (RPD) [anterior–posterior diameter (APD) 10–15 mm] in an unselected population of 2-month-old infants prospectively followed for up to 12–14 months of life. Isolated moderate renal pelvis dilatation was detected in 282 of the 11,801 (2.4%), infants screened; 240 infants with normal renal ultrasound were enrolled as the control group. Resolution of RPD was considered when an APD ≤ 5 mm was found on two consecutive sonograms. Urological investigations were initiated if the RPD persisted or if urinary tract infection (UTI) occurred during follow-up, and antibiotic therapy was administered only when UTI occurred. The events of interest were resolution of the RPD, presence of uropathy and UTI. At follow-up, RPD persisted only in 18 infants; of these, four infants were diagnosed with vesicoureteral reflux (grade 1–3) and 14 with ureteropelvic junction obstruction. Of the 223 infants with RPD and 230 control infants who completed follow-up, UTI occurred in 3.6 and 2.5%, respectively. The incidence rate of UTI per 1000 person-months was 5.98 episodes in the patient group and 5.22 episodes in the control group. The rate ratio was 1.146 (95% confidence interval 0.389–3.54, p = 0.8). Our data suggest that isolated moderate RPD is essentially a self-limiting condition and that antibiotic prophylaxis for the prevention of UTI should not be performed. A non-invasive ultrasound scan performed during the follow-up is sufficient to diagnose a potentially dangerous and persistent RPD.