Evaluation of renal resistive index, maximum velocity, and mean arterial flow velocity in a hydronephrotic partially obstructed pig model.

RATIONALE AND OBJECTIVES: The authors investigate, in a controlled pig model, the usefulness of Doppler sonographic measurements of resistive index (RI), maximum velocity (Vmax), and mean velocity (Vmean) in diagnostic evaluation of the partially obstructed kidney. METHODS: Seven female pigs underwent surgical partial unilateral renal obstruction at the ureteropelvic junction. Doppler parameters of RI, Vmax, and Vmean were measured preoperatively and postoperatively in obstructed and contralateral nonobstructed kidneys. The General Linear Model multivariate analysis of variance was used for statistical analysis of data. RESULTS: There was no significant difference in the preoperative control values of RI (P = 0.71), Vmax (P = 0.27), and Vmean (P = 0.12). There was a statistically significant decrease in the Vmax and Vmean after postoperative day 5 in the obstructed kidney compared with the contralateral nonobstructed kidney (P = 0.01 and 0.03, respectively). There was no statistically significant difference in RI during the study. CONCLUSIONS: In this study, RI was not a reliable indicator of partial renal obstruction. Measurements of maximal and mean blood flow velocities reached discriminatory significance only after the fifth postobstructive day, proving insensitive in the immediate postobstructive period. Vmax and Vmean demonstrated a decrease in the partially obstructed renal collecting system after 5 days of obstruction and may serve as useful parameters in the evaluation of obstruction after the immediate acute period, when compared with a nonobstructed contralateral system.

The value of Doppler resistive index and peak systolic velocity in the evaluation of porcine renal obstruction.

PURPOSE: We evaluated the use of Doppler resistive indexes and systolic velocities as diagnostic tools in a partially obstructed animal model. MATERIALS AND METHODS: We studied 12 normal pigs by Doppler sonography, which served as control units. In 9 subjects partial ureteral obstruction was then created surgically, and 3 continued as controls. The presence or absence of obstruction was confirmed by ultrasound, antegrade nephrostography and intrapelvic pressure monitoring. Doppler parameters were measured 1 hour to 21 days postoperatively. Resistive index, and angle corrected peak and mean systolic velocities were measured bilaterally from samplings of interlobar and arcuate arteries. An average of 4 samplings per kidney was obtained at each session. Data from the control and obstruction groups were compared for statistical differences. RESULTS: In controls mean resistive index was 0.53, and peak and mean systolic velocities were 0.38 and 0.26 m. per second, respectively. In the subacute period after obstruction (defined as days 4 to 21) mean resistive index was 0.54, and peak and mean systolic velocities were 0.33 and 0.22 m. per second, respectively. Compared to control data there was no significant change in resistive index after obstruction (p = 0.6). However, peak and mean systolic velocities showed significant downward trends (p < 0.05). CONCLUSIONS: Known small sequential changes in renal blood flow after ureteral obstruction are reflected in flow velocities, as measured by duplex Doppler sonography. However, resistive indexes are not useful in assessing these changes in renal blood flow, and they do not correlate with the presence or absence of obstruction in this animal model.