Intrarenal duplex Doppler sonographic evaluation of unilateral native kidney obstruction.

RIs were measured in intrarenal arteries in 66 kidneys of 33 examinees without renal impairment and in 42 kidneys of 21 patients with unilateral urinary obstruction. The mean RI in normal kidneys was 0.593 +/- 0.040. Patients with unilateral obstruction had a mean RI of 0.709 +/- 0.039 in obstructed kidneys and a mean RI of 0.591 +/- 0.033 in contralateral nonobstructed kidneys. Statistically significant differences have been noticed in the groups of normal versus obstructed kidneys (P < 0.001) and of obstructed versus contralateral nonobstructed kidneys (P < 0.001). The mean dRI was 0.118 +/- 0.034 in patients with unilateral obstruction, and it was 0.014 +/- 0.012 in examinees without renal impairment (P < 0.001). A comparison of RI values between the right and left kidneys in a patient with unilateral obstruction proved more useful than using a 0.7 RI cutoff value in a Doppler sonographic diagnosis of unilateral obstruction.