Comparison of imaging characteristics on computed tomography and magnetic resonance urography in urological conditions

Introduction: Urinary tract (UT) pathologies are common causes of morbidity presenting mainly as acute flank pain, obstructive uropathy, and hematuria with calculus being the commonest cause. Computed tomography (CT) (noncontrast, contrast enhanced and urography) of the kidney, ureter, and bladder region has been considered as the mainstay in evaluation of patients with UT symptoms. Limitations of radiation exposure and risks of contrast injection in CT have provided space for magnetic resonance urography (MRU) that has recently gain acceptance. However, MRU is limited by its availability and higher cost. Thus, with the aim of evaluating the scope of MRU in various UT pathologies, we planned a comparative study between CT scan and MRU. Materials and Methods: Thirty-five patients with UT symptoms (acute flank pain, obstructive uropathy, and hematuria) were evaluated with CT scan and MRU after obtaining approval from Institutional Ethics Committee and written informed consent from the participants of the study. CT scan was performed on 128-slice CT scanner while MRU was performed on 1.5T magnetic resonance scanner using the standard protocol. The data thus recorded in a single-blinded manner were analyzed using appropriate statistical methods and tools. Results: Compared with CT scan, MRU had a poor accuracy in detecting UT stones especially <6 mm and without secondary signs of obstruction. However, MRU performed very well in patients with obstructive uropathy and hematuria subgroup with no significant difference in accuracy from CT scan. Overall, MRU had a moderate sensitivity of 76.3%, high specificity of 96.9% and moderately high accuracy of 85.7%. Conclusions: Although MRU has lower sensitivity to small sized UT calculus but is very specific to secondary signs of obstruction as well as to causes of obstructive uropathy and hematuria. It can serve as an excellent alternative tool especially in patients with contraindication of contrast injection in CT scan as well as in children, during pregnancy and in conditions requiring repetitive examinations.