Abstract / Summary
BackgroundObstructive uropathy is a common condition that can damage the kidneys if it is not detected and treated early.Appropriate imaging is needed to identify the location and cause of the obstruction.Computed tomography urography (CTU) is widely used for evaluating urinary tract obstruction, while non-contrast magnetic resonance urography (MRU) may provide an alternative when ionizing radiation or iodinated contrast is undesirable. AimTo prospectively compare CTU and non-contrast MRU for the accurate identification of the cause and level of obstruction against an intervention-based reference standard in patients with suspected obstructive uropathy. Materials and methodsThis observational study was carried out over two years (January 2023-December 2024) in the Department of Urology, King George Hospital, Visakhapatnam.We prospectively enrolled 30 eligible patients during the study period.Each patient underwent both CTU and non-contrast MRU, allowing a paired within-patient comparison.CTU and MRU were performed within two weeks of each other and were interpreted by different blinded radiologists.The intervention was performed within one week of MRU.The reference standard consisted of intervention findings or histopathology in 29 patients and follow-up in one patient. ResultsAgainst the reference standard, CTU correctly identified both the cause and level of obstruction in 30 of 30 patients (100%), while MRU correctly identified both in 28 of 30 patients (93.3%).Both modalities identified all 17 calculi, seven strictures, and three urothelial or bladder tumors.Of the three congenital cases (pelviureteric junction (PUJ) obstruction or megaureter), CTU identified all three, while MRU identified one. ConclusionIn this prospective cohort, non-contrast MRU correctly identified the cause and level of urinary tract obstruction in 28 of 30 patients, compared with 30 of 30 for CTU.The two MRU failures involved congenital abnormalities: primary obstructive megaureter and PUJ obstruction with crossed fused renal ectopia.The study was not designed to test equivalence or non-inferiority of MRU to CTU.Non-contrast MRU could be an alternative for selected patients to avoid radiation or iodinated contrast.Larger multicentre studies with standardized protocols, blinded interpretation, and independent reference standards are needed.