Normal and hydronephrotic kidney: evaluation of renal function with contrast-enhanced MR imaging.

Four healthy volunteers and six patients with hydronephrosis underwent magnetic resonance (MR) imaging after the injection of gadolinium-diethylenetriaminepenta-aceticacid for the assessment of renal function. Coronal angulated 10-second images were obtained during suspended respiration (inspiratory apnea) and showed excellent anatomic detail. In healthy volunteers, the renal cortex showed an increase in signal intensity after Gd-DTPA injection, and the renal medulla showed a precipitous decrease in intensity approximately 1 minute after injection, followed by a gradual increase in intensity. The renal pelvis showed a gradual decrease in intensity after several minutes, with occasional signal-void areas in adjacent structures. In patients with hydronephrosis, the decrease in intensity in the medulla and pelvis was not observed; instead, an increase in intensity occurred. The physiologic function of glomerular filtration and in vitro results of serial dilutions of Gd-DTPA suggest that the decrease in intensity is due to T2 and susceptibility effects occurring at high concentrations of Gd-DTPA.