MR urography in the diagnosis of urinary tract obstruction

Objective: To evaluate the efficiency of MR urography in depicting the urin ary tract. Methods: 33 patients with urinary tract abnormalities were addit ionally evaluated with MR urography. 25 had dilated upper urinary tracts be cause of urinary obstruction and 8 had normal tracts. MR urography was perf ormed with a 1,5T magnet using a heavy T2w sequence (3D-IR-TSE) in the coro nal plane. Images were post-processed using the MIP algorithm. Both reconst ructed and source images were evaluated. The results of MR urography were c ompared with the final diagnosis, which was established surgically in 23 ca ses, and with multimodality imaging workup in 10 cases. Results: MR urograp hy correctly depicted the level of obstruction and the degree of dilatation of the urinary tract in all 25 patients with hydronephrotic kidneys (sensi tivity 100%). Additionally, it succeeded in suggesting the underlying patho logy in 25 cases (48%). Concerning the 8 patients without dilatation of the urinary tract, there was either no depiction or depiction was bad. Conclus ion: MR urography, a new noninvasive technique, demonstrates 100% sensitivi ty in diagnosing urinary tract obstruction and also suggests the underlying pathology in many cases. In nondilated systems it is not possible to get g ood images because MR urography only depicts fluid in the urinary tract. Th us we believe that MR urography can provide a reliable alternative in selec ted cases as opposed to other more invasive modalities, such as retrograde or antegrade urography, and is without the risk of contrast media and radia tion exposure.