Objective: This study was designed to characterize the resistive index (RI) of prostatic blood flows obtained by transrectal power Doppler sonography (TRPDS) in benign prostatic hyperplasia (BPH).
Method: In 140 patients with lower urinary tract symptoms, the RI was measured using TRPDS and compared with age and planimetric parameters of the prostate obtained by conventional transrectal sonography. In addition, the RI was related with pressure flow studies.
Results: The RI was significantly higher in patients with BPH (0.72+/-0.06, p<0.0001) than those with a normal prostate (0. 64+/-0.04). Although the RI correlated significantly with age and all prostatic planimetric parameters, multiple regression analysis revealed that age and presumed circle area ratio were independent predictors for RI. The RI was also higher in patients with infravesical obstruction than those without (0.74+/-0.06 vs. 0. 70+/-0.05, p<0.005). There was a significant correlation between RI and urodynamic parameters obtained in pressure flow studies. Out of 33 patients with obstruction, 28 (85%) had an RI of 0.7 or more, while 11 out of 24 patients (46%) without obstruction had an RI less than 0.7.
Conclusion: The RI is promising as a new parameter to estimate the intraprostatic pressure to investigate BPH. Its value to represent urodynamic information during voiding remains to be studied.