Division of Nuclear Medicine, Department of Radiology, Hospital of the University of Pennsylvania, PA, USA
The common use of maternal ultrasonography has increased the apparent incidence of neonatal hydronephrosis. Many of these cases are found to have partial obstruction at the ureteropelvic junction (UPJ). These patients are safely managed in our institution with careful observation and only occasionally require surgical intervention. The authors present two contrasting cases of suspected UPJ obstruction in the neonatal period. The diagnostic evaluation and management in these two patients with similar presentation and markedly different outcome are discussed. The role of various imaging modalities including voiding cystourethrography (VCUG), intravenous pyelography (rVP), ultrasonography (US) and diuretic radionuclide renography was discussed. The relationship of normalized renal uptake and diuretic clearance half-time (Tl/2) with outcome was examined in 50 patients with prenatally diagnosed hydronephrosis. The normalized uptake value is the fraction of the total Tc99m DTPA extracted by each kidney between 60 and 120 seconds following the injection of the patient There was a statistically significant difference in the renal uptake and Tl/2 in those kidneys that subsequently required surgery compared to those wtich were managed conservatively. The predictive value of renal uptake and Tl/2 in identifying those patients who require surgical correction is not yet fully defined.