Visualization of urinary tract dilatation: value of single-shot MR urography.

The purpose of this study was to evaluate detection of urinary tract dilatation, depiction of obstruction level and determination of cause with single-shot MR imaging in an acquisition time of 2.8 s. Heavily T2-weighted single-shot MR images in 50 patients with ureterohydronephrosis as suspected by ultrasound were prospectively compared with IV urography and clinical outcome. Imaging techniques were obtained within a maximum time interval of 4 h and assessed independently on the same day. Single-shot MR urography was able to demonstrate dilatation and obstruction levels in 96 % of urinary tracts in accordance with X-ray urograms. In 4 patients with a unilaterally negative IV urogram, obstruction levels were demonstrated in single-shot MR urography. Single-shot MR urography did not depict 2 of 7 collecting systems with mild dilatation and contralateral undilated ureters were not adequately visible. Single-shot MR urography consistently visualizes dilated urinary tracts and obstruction levels in moderate and severe dilatation. Single-shot MR urography may be an alternative for IV urography in cases of renal impairment, when iodinated contrast or the application of X-rays is contraindicated, and may help in avoiding direct ureteropyelography. Single-shot MR urography rarely allows determination of the cause of urinary tract dilatation.