MR urography in evaluation of acute flank pain: T2-weighted sequences and gadolinium-enhanced three-dimensional FLASH compared with urography

OBJECTIVE. The aim of this study was to compare the usefulness of breath-ho ld heavily T2-weighted sequences with gadolinium-enhanced three-dimensional fast low-angle shot (3D FLASH) MR urography in the evaluation of patients with acute flank pain. SUBJECTS AND METHODS. Forty consecutive patients with symptoms of acute fla nk pain underwent MR urography followed immediately by excretory urography. Heavily T2-weighted (combined thin-slice half-Fourier acquisition single-s hot turbo spin-echo [HASTE] and thick-slab single-shot turbo spin-echo) and 3D FLASH sequences were evaluated separately and independently by two expe rienced radiologists for the presence, cause, level, and degree of obstruct ion. Interobserver agreement was calculated using the kappa statistic. Excr etory urography and the final clinical diagnosis were used as reference. RESULTS. Twenty-six patients were found to have unilateral obstruction caus ed by ureteral stones. Both MR urography methods were excellent for detecti ng obstruction. In the detection of stones 3D FLASH was superior, with a se nsitivity of 96.2% and 100% and specificity of 100% and 100% for observers A and B, respectively, compared with a sensitivity of 57.7% and 53.8% and a specificity of 100% and 100%, respectively, for T2-weighted sequences. The best degree of obstruction was seen with 3D FLASH, and the interobserver a greement was excellent for stone detection (kappa = 0.97). CONCLUSION. T2-weighted sequences alone are not sufficient for examining pa tients with acute flank pain. However, the combined use of both T2-weighted and 3D FLASH sequences will ensure better confidence in the evaluation of acute suspected renal colic. MR urography can replace conventional excretor y urography when the latter is contraindicated or undesirable.