Congenital anomalies occur in 2% to 3% of all neonates and are a major cause of perinatal morbidity and mortality. Prenatal ultrasonography can detect most fetal malformations. Current diagnostic capabilities can identify urinary tract anomalies as early as 12 to 14 weeks of gestation.<sup>9 Bronshtein M. , e al. First and early second-trimester diagnosis of fetal urinary tract anomalies using transvaginal sonography Prenatal Diagnosis 1990 ;  10 : 653  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> The detection rate of urologic abnormalities with prenatal ultrasonography ranges from 84.4%<sup>56 Zimmer E.Z. , e al. Influence of prenatal ultrasound on the prevalence of congenital anomalies at birth Prenatal Diagnosis 1997 ;  17 : 623-628  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> to 97%.<sup>17 Corteville J.E., Gray D.L., Crane J.P. Congenital hydronephrosis: Correlation of fetal ultrasonographic findings with infant outcome Am J Obstet Gynecol 1991 ;  165 : 384-388

Cliccare qui per andare alla sezione Riferimenti</sup> The ability to diagnose abnormalities of the fetal urinary tract with the widespread use of routine obstetric ultrasound examinations has contributed to the growth of perinatal urology. Contemporary ultrasonographic techniques cannot directly confirm the existence of obstruction, a physiologic attribute, but rather demonstrate dilation as an imaging characteristic only. Current understanding of the pathophysiology of obstructive uropathy is incomplete, and there is considerable controversy in regards to what constitutes clinically significant obstruction and in regards to the indications and optimal timing of surgical intervention in the management of prenatally diagnosed cases of ureteropelvic junction (UPJ) obstruction.

Increased information on antenatally detected asymptomatic UPJ obstruction has altered the understanding of the natural history of this condition. In the past, most patients presented with symptoms such as urosepsis, pain, hematuria, a palpable mass, or failure to thrive such that the need for treatment was apparent. However, the management of incidentally detected hydronephrosis continues to evolve. It is now apparent that not all urinary tract dilatation is secondary to mechanical obstruction but may simply be the result of an atonic collecting system.<sup>43 Merguerian P. The evaluation of prenatally detected hydronephrosis Monogr Urol 1995 ;  16 (3) : 1-5

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Initial experimental and clinical evidence suggested that early relief of congenital urinary obstruction was associated with a significantly greater return of renal function through recruitment of immature nephrons in the peripheral cortical zone.<sup>24 Fink R. , e al. Renal impairment and its reversibility following variable periods of complete ureteric obstruction Aust NZ J Surg 1980 ;  50 : 77-81  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> This concept was supported by evidence showing that renal development continues throughout infancy, with glomerular filtration rate (GFR) and creatinine clearance reaching adult levels by the age of 2 years. Conservative management of these incidentally detected anomalies has become the standard of care, with no long-term loss of measurable renal function in the majority of cases.<sup>48 Ransley P.G., Manzoni G.A. `Extended' role of DTPA scan in assessing function and UPJ obstruction in neonate Dialog Pediatr Urol 1985 ;  8 : 6-8

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