We aimed to assess the hemodynamic effects of nonionic low-osmolarity contrast media (CM) on kidneys with ureteral stone (KUS). A total of 16 patients with KUS (group A) and 25 control patients (group B) were evaluated with Doppler ultrasound (US) bilaterally for main (MRA), interlobar (ILA) and arcuate renal arteries (ARA), before and 15 min after CM for IV pyelography. Peak systolic (PSV) and end diastolic velocities (EDV) and resistance index (RI) were measured. Data were analyzed by ANOVA and t-test. In group A. CM induced increase in PSV of MRA of contralateral kidney (p = 0.021) and decrease in PSV of ILA (p = 0.024) decrease in PSV and EDV and increase in RI of ARA of KUS (p = 0.010. 0.005. 0.027. respectively). CM induced hypoperfusion in KUS and compensatory changes in contralateral kidneys. similar to the effects of diuresis or mannitol. We conclude that the effect of CM on KUS is related to its osmolar load. (C) 2005 World Federation for Ultrasound in Medicine Biology.