Influence of posture change on intrarenal arterial resistive index measurement

Background: We investigated the influence of posture change on intrarenal arterial resistive index measurement in 80 subjects (38 male, 42 female). Methods: Three interlobar arteries in the superior, middle, and inferior parts of the right kidney in each subject were examined by color Doppler ultrasound in two different positions (left lateral decubitus and supine). Based on the movement of the kidney caused by posture change, 23 subjects were classified as having a highly mobile kidney (group I) and the other 57 subjects were classified as not having a highly mobile kidney (group II). Results: Fifty-eight kidneys (72.5%), 19 in group I (82.6%) and 39 in group II (68.4%), showed higher resistive index values in the lateral decubitus position than in the supine position. The influence of posture change on resistive index measurement was significant ( p < 0.001 for all subjects, p < 0.01 for group I, p < 0.05 for group II). The ranges of resistive index differences caused by posture change were 0–0.13 for group I and 0–0.11 for group II. The difference in resistive index caused by posture change was not significant between groups. Conclusion: Posture change is a potential confounding factor for intrarenal resistive index measurement.