<title>ABSTRACT</title><sec><title>Purpose:</title><p>To determine the renal arterial hemodynamic changes induced by obstructive uropathy using Doppler ultrasonography.</p></sec><sec><title>Materials and Methods:</title><p>60 adult subjects with suspected obstructive uropathy and 60 asymptomatic apparently healthy controls with normal renal ultrasound features were evaluated.</p><p>B-mode sonography of the kidneys and spectral Doppler examination of the renal interlobar arteries of all the participants were performed. The mean resistive indices (mRI) of both interlobar arteries were obtained and compared to that of the controls. The mRI of bilaterally obstructed kidneys were also compared with the mRI of unilaterally obstructed kidneys.</p></sec><sec><title>Results:</title><p>The mRI of the right and left kidneys of subjects were 0.72±0.04 and 0.69±0.06 while those of the controls were 0.64±0.04 and 0.63±0.03 respectively. The mRI for the grades of caliectasis increased from grade I (0.72±0.03) to grade II (0.73±0.03) and grade III (0.73±0.02) but fell within the most severe levels of obstruction (0.69±0.07). There was no statistically significant relationship between the grades of caliectasis and unilateral or bilateral obstruction for both kidneys. The results show a sensitivity and specificity of 86.7% and 90% respectively when mRI≥0.7 was used to determine presence of obstruction.</p></sec><sec><title>Conclusion:</title><p>Renal duplex sonography is highly sensitive and specific for diagnosis of obstructive uropathy. Increased resistive index of the obstructed kidney may be a useful diagnostic tool in situations where intravenous urography cannot be done or is contraindicated.</p></sec>