MR urography: evaluation of a three-dimensional fast spin-echo technique in patients with hydronephrosis

The purpose of this study was to evaluate a respiratory-triggered three-dimensional (3D) fast spin-echo technique for MR urography in patients with urinary tract dilatation.

Using a respiratory-triggered 3D fast spin-echo technique for MR urography, we obtained MR urograms in 24 patients with hydronephrosis. Images were separately reviewed by two radiologists who evaluated the images for quality, presence of, degree of, level of, and cause of urinary tract dilatation. Findings were compared with all available clinical, imaging, surgical, and pathologic data, which served as the standard of reference. Sensitivity, specificity, positive predictive value, and negative predictive value of MR urograms were calculated for each reviewer to reveal urinary tract dilatation. For each reviewer, we calculated agreement between MR urography and the standard of reference using kappa analysis. We also calculated interobserver agreement for the presence of degree of, level of, and cause of urinary tract dilatation.

Technically adequate MR urograms were obtained in all patients. For detection of urinary tract dilatation by MR urography, the sensitivity was 100%; specificity was 96%; positive predictive value was 96%; and negative predictive value was 100%. The kappa values for the degree of dilatation seen on the MR urograms were 0.57 (moderate) and 0.43 (moderate); for the level of obstruction, 0.74 (substantial) and 0.55 (moderate); and for the cause of obstruction, 0.66 (moderate) and 0.66 (moderate). Interobserver agreement for seeing dilatation on MR urograms was 1.0 (perfect agreement); degree of dilatation, 0.48 (moderate); level of dilatation, 0.60 (moderate); and cause of dilatation, 0.74 (substantial).

MR urography using a respiratory-triggered 3D fast spin-echo technique can produce high-resolution images of the urinary tract by which reviewers can achieve a high sensitivity (100%) and specificity (96%) for the detection of urinary tract dilatation. On MR urograms, reviewers also identified the cause of obstruction in most patients: 92% (reviewer 1) and 88% (reviewer 2).