Magnetic resonance urography enhanced by gadolinium and diuretics: a comparison with conventional urography in diagnosing the cause of ureteric obstruction.

OBJECTIVE: To compare the ability of magnetic resonance urography (MRU), enhanced using gadolinium and frusemide diuresis, and conventional intravenous urography (IVU) to diagnose the cause of ureteric obstruction.

PATIENTS AND METHODS: The study included 82 patients in whom IVU showed or suggested obstruction and who also underwent MRU. The images from both methods were interpreted by various investigators independently; two evaluated the IVU and two others the MRU, the latter being unaware of the diagnosis after IVU. If the diagnosis remained unclear, further investigations (e.g. computed tomography, retrograde pyelography or ureteroscopy) were conducted.

RESULTS: The diagnoses were ureteric calculi in 72 patients, ureteric tumours in eight and extra-ureteric tumours in two. In those with urolithiasis, the diagnosis was correct with IVU in 49 patients and with MRU in 64. The diagnosis in this group was incorrect with MRU in only two patients. The main reason for the failure of IVU was absent contrast medium excretion. Three of eight patients with ureteric tumours were correctly diagnosed by IVU but in three patients the diagnosis was incorrect. MRU correctly diagnosed seven of the eight patients in this group, with no false diagnosis.

CONCLUSION: IVU is currently likely to remain the standard procedure for imaging the upper urinary tract, but this study shows the potential of MRU when enhanced with gadolinium and frusemide. MRU may be helpful if there is a dilated system with no excretory function, in pregnant women, in children and in those with contrast medium allergy.