Clinical outcome is associated with the Urinary Tract Dilatation Classification System grade.

To assess the association between the Urinary Tract Dilatation (UTD) Antenatal (A) and Postnatal (P) Classification System grade and the outcome in term newborns. This retrospective study enrolled 166 term newborns (71% boys, 206 ureterorenal units) evaluated for unilateral or bilateral UTD in the Neonatology Department of Ljubljana University Medical Center from 2012 to 2018. Data on family history, sex, gestational age, birth weight, head circumference, Apgar score, possible oligohydramnios, indication for and age at first postnatal ultrasound, time of follow-up, and clinical outcome were collected. Radiology records were reviewed to grade UTD according to the Multidisciplinary Consensus on the Classification of Prenatal and Postnatal UTD. The majority of ureterorenal units with UTD A 2-3 had UTD P 2 or 3. Spontaneous resolution, specific uropathy, the need for surgery, and the risk of urinary tract infection were all significantly associated with the UTD P grade. No patient experienced renal dysfunction at the end of follow-up (12-48 months, median 24 months), and therefore this parameter was not associated with the UTD P grade. The UTD grade was associated with the probability of spontaneous resolution, time to its occurrence, specific uropathies urinary tract infection, and risk for surgery. However, no association with renal dysfunction was established.