administered, with a time-intensity curve of each kidney produced. Drainage was diagnosed by a clearly declining timeintensity curve and direct visualization of contrast medium within the ureter in several frames. High-grade or complete obstruction was diagnosed when drainage of contrast medium could not be detected. Gd-MRU results were compared with diuresis radionuclide (mercaptoacetyltriglycine, MAG3) renography within the same week. Unobstructive units detected by Gd-MRU were treated conservatively with a close follow-up by ultrasonography and radionuclide studies.
RESULTSDiuresis MAG3 renography showed drainage in three dilated units and poor washout in five; in contrast, Gd-MRU showed drainage in seven dilated systems (three showed poor washout by MAG3), and obstruction in the remaining case. The unobstructed units detected by MRU under conservative treatment thus showed no further deterioration of renal function or progressive hydronephrosis in the subsequent follow-up (mean 18 months, range 15-23).
CONCLUSIONThese preliminary results suggest that dynamic Gd-MRU is a useful noninvasive imaging method in distinguishing obstructive from unobstructive dilated systems, particularly in patients with hydronephrosis and reduced renal function.