RESUMEN
BACKGROUND: Fetal hydronephrosis is the most common anomaly detected on antenatal ultrasound examination, affecting 1-5% pregnancies. AIM: A new management in mild antenatal renal pelvis dilatation (ARPD), using a technique based on both morphological and dynamical evaluation. MATERIALS AND METHODS: Prospective study conducted during a 36-months period in 180 consecutive newborns referred as having mild ARPD. Examinations consisted in a morphological ultra-sound (US) scan evaluating antero-posterior diameter, renal parenchyma, ureteral evidence and pelvis morphology and, subsequently, a dynamic evaluation to analyze any change of the urinary tract during bladder voiding. All children were evaluated both at 3rd day and 1 month after birth. They were divided among those with negative examinations and those with at least one positive scan, trying to discriminate within the latter, children suspected for transient pyelectasis from those suspected for organic pathology. RESULTS: 108 patients had normal US findings both at birth and at 1 month. The remaining 72 babies had at least one abnormal US examination: 54 were suspected for transient pyelectasis, while 18 suspected for organic pathology. At the end of the study, 61 babies (33.9%) had final diagnosis of transient pyelectasis and 11 cases (6.1%) of organic pathology. At one month the dynamic pattern of US findings had the highest negative predictive value, while renal parenchyma evaluation has the highest accuracy. CONCLUSIONS: a dynamic US approach allowed to better select among infants suspected for transient pyelectasis from those suspected for organic pathology, avoiding unnecessary and invasive examinations in healthy babies.