Magnetic Resonance Urography in Patients with Non- Contributory Intravenous Urography

Magnetic Resonance Urography (MRU) is increaingly replacing Intravenous Urography (IVU) which has been the traditional modality for uro-imaging. However, the effectiveness and advantages of this new and costly modality need to be proven before defining its place in the uro-radiological armamentarium. We conducted a prospective study to assess the role of MRU in 100 consecutive cases where IVU was inconclusive or contra-indicated. As 4 patients had solitary functioning kidney, a total of 196 renal units were evaluated. In all the cases the results of IVU and MRU were cross-checked for accuracy by multimodality imaging or surgical feedback. The Sensitivity, Specificity and the Predictive Value of a positive and negative MRU were calculated. Since the study was conducted in cases where IVU was non-contributory , MRU was evaluated as a stand-alone test. We found that with the exception of diagnosing stone disease in non-obstructed renal units, MRU is an excellent modality for evaluating the renal system. It can be successfully used to image paediatric and pregnant cases. It can rapidly demonstrate the pelvicalyceal system even in renal units with deranged excretion. It can be used in emergency settings on unprepared patients. Its efficacy is reduced in non-dilated renal units.