Resistive index as risk factor for acute urinary retention in patients with benign prostatic hyperplasia.

OBJECTIVES

To examine the usefulness of several parameters obtained by transrectal ultrasonography in predicting acute urinary retention (AUR).

METHODS

The present study consecutively enrolled 1962 men with a complaint of lower urinary tract symptoms. Of these men, 245 were found to have AUR on examination at our clinic. We assessed the International Prostate Symptom Score (IPSS), maximal urinary flow rate, and postvoid residual urine volume and measured the total prostate volume, transition zone index (TZI), and resistive index (RI) using transrectal ultrasonography. To compare the usefulness of these indexes for predicting AUR, we calculated the area under the receiver operating characteristic curve for each index and for age.

RESULTS

In patients without AUR, age, prostate-specific antigen level, IPSS, maximal urinary flow rate, and postvoid residual urine volume were significantly correlated with both the TZI and the RI (P < .001). Multiple regression analysis demonstrated that age, maximal urinary flow rate, postvoid residual urine volume, and TZI were significant independent determinants of the RI (P < .001). Patients with AUR were, on average, older and had an elevated prostate-specific antigen level, increased IPSS, and greater TZI and RI than patients without AUR (P < .001). The area under the receiver operating characteristic curve was 0.640 (95% confidence interval [CI] 0.618-0.662) for age, 0.674 (95% CI 0.653-0.695) for prostate-specific antigen level, 0.787 (95% CI 0.768-0.805) for total prostate volume, 0.821 (95% CI 0.803-0.838) for IPSS, 0.860 (95% CI 0.844-0.875) for TZI, and 0.867 (95% CI 0.851-0.882) for RI.

CONCLUSIONS

The RI and TZI obtained using transrectal ultrasonography correlated with the incidence of AUR and are useful predictors of AUR in patients with benign prostatic hyperplasia.