Magnetic resonance pyelography: clinical use of ultrafast breath-hold sequences in obstructive uropathy. Personal experience.

INTRODUCTION: We investigated the diagnostic yield of MR pyelography (MRP) performed with two ultrafast breath-hold sequences in obstructive uropathy patients. MATERIAL AND METHODS: Thirty-four patients with US demonstration of urinary tract dilation were examined with MRP at 1.5 T and with a standard body coil. HASTE sequences (TE 66, ETL 128, FA 180 degrees, 1 NEX, MA 240 x 256, slice thickness 4 mm, TA 13 s) were always performed and 26/34 patients were also examined with single-shot TSE sequences (TE 1100, ETL 240, FA 150 degrees, 1 NEX, slice thickness 7 cm, MA 240 x 256, FS, TA 7 s); 20/34 patients were given 500 mL superparamagnetic contrast agent (Lumirem). MRP findings were interpreted independently by two radiologists and analyzed for image quality, the presence/absence of dilation, the obstruction grade (mild, moderate, severe), site (intrarenal; ureteropelvic junction; proximal, mid-, distal ureter; indeterminate) and cause (intrinsic obstruction from a stone or other conditions; stenosis; indeterminate cause). The sensitivity, specificity, positive and negative predictive values for the detection of urinary tract dilation were calculated for each reviewer and interobserver agreement was calculated with the k analysis relative to the presence, grade, site and cause of urinary tract dilation. RESULTS: MRP examinations were considered technically adequate in all cases by both observers. As for the presence of urinary tract dilation, the values were 100% for the first observer and 97%, 100%, 100%, and 95%, respectively, for the second observer. Interobserver agreement was .98 for dilation presence (excellent), .80 for dilation degree (excellent), .62 for dilation site (good) and finally .69 for dilation cause (good). DISCUSSION AND CONCLUSIONS: MRP performed with the ultrafast breath-hold technique provides very good results in diagnosing urinary tract dilation, as well as the obstruction grade, site and cause, with results equal or even superior to those of non-breath-hold sequences. Ultrafast MRP lasts only 10 minutes, meaning it occupies the magnet shortly and costs less: it can be thus considered a routine alternative to conventional diagnostic imaging, especially ivp, in the evaluation of obstructive uropathy.