Abstract

Introduction: Intravenous urography is the standard method in the diagnostic workup of most urinary tract diseases. It is a relatively cheap technique and easily available. Information about the function and anatomy of the kidneys can be obtained, however, it has some disadvantages like ionising radiation exposure and it needs intravenous contrast injection. Magnetic resonance is a relatively new method and its application areas are increasing. Static fluids can be shown by heavily T2-weighted images in MR imaging. This technique has been used for MR cholangiopancreatography and MR myelography. Same method can also be used in urinary tract imaging. In this study, we evaluated the effectiveness of MR urography in the evaluation of urinary obstructive diseases.

Materials and Methods: We evaluated 67 kidneys in 34 patients. Twenty-five of them were male and 9 were female. Their age ranged between 4-64 years and mean age was 48.4 years. All patients had unilateral or bilateral urinary system dilatation confirmed by IVP, US or CT. All these patients underwent MR urography within 1-3 days after other radiologic examinations. No patient preparation was made before MR urography and no medication was given before or during the MR examination. Compression was not applied during the scans. For MR urography, heavily T2 weighted three dimensional fast spin echo sequences were used. Reconstructed images were also obtained by maximum intensity projection algorithm. MR urograms were evaluated by two radiologist for the presence of dilatation. If dilatation is present, the level and cause of this dilatation were also noted. MR urography findings were compared with final diagnoses of the patients. Sensitivity, specificity, positive and negative predictive values of MR urography in the detection of urinary dilatation was estimated. As well, correlation of IVP and MR urography for the detection of obstruction level was evaluated by Kappa analysis.

Results: In forty kidneys, presence of dilatation was confirmed by IVP, US or CT. MR urography showed dilatation in 39 of these kidneys. There was only one false negative result and no false positive result. The sensitivity, specificity, positive predictive and negative predictive values of MR urography for the detection of dilatation were 97%, 100%, 100% and 96%, respectively. Correlation of IVP and MR urography was good (Kappa=0.805) for the detection of dilatation degree. Correlation of IVP and MR urography was very good (Kappa=0.877) for the detection of obstruction level.

Conclusion: Our findings suggest that, in selected cases, MR urography may be used as an alternative or complimentary method in the evaluation of urinary obstruction.