Diffusion-weighted MR imaging and Doppler ultrasonography in the evaluation of renal parenchyma in acute ureteral obstruction.

OBJECTIVE To compare the efficacy of diffusion-weighted (DW) magnetic resonance (MR) imaging and Doppler ultrasonography (US) by using quantitative markers in acute unilateral obstruction due to renal stones. METHODS This prospective study included 28 patients with unilateral ureteral obstruction and 18 healthy control subjects. In Doppler US and DW MR imaging, resistive index (RI) and apparent diffusion coefficient (ADC) values were measured respectively. The results were compared in patients and in control subjects. Paired samples test, two-tailed unpaired Student's t test and Spearman analysis were performed for statistical analysis. RESULTS The mean RI in the 28 obstructed kidneys was significantly higher than the mean RI in unobstructed kidneys and in control subjects (P < 0.05). The ADC of obstructed kidneys in the cortex was significantly lower than the ADC of the contralateral unobstructed kidneys (P < 0.05). The ADC of unobstructed kidneys was significantly higher than the ADC of control subjects in the cortex (P < 0.05). RI and ADC values yielded no significant correlation. CONCLUSION Doppler US and DW MR imaging provide accurate and noninvasive diagnosis, Doppler US may be preferred as it is a more practical technique compared to DW MR imaging in the evaluation of acute ureteral obstruction due to renal stones.