Combination of intravesical prostatic protrusion and resistive index is useful to predict bladder outlet obstruction in patients with lower urinary tract symptoms suggestive of benign prostatic hyperplasia.

Abstract

To examine which parameters obtained from transrectal ultrasonography are accurate predictors of urodynamically-confirmed bladder outlet obstruction in patients with lower urinary tract symptoms suggestive of benign prostatic hyperplasia. The records of 350 patients with complaints of lower urinary tract symptoms suggestive of benign prostatic hyperplasia were reviewed. Baseline parameters were international prostate symptom score, quality of life score, postvoid residual urine volume, prostate-specific antigen, and data obtained from uroflowmetry and transrectal ultrasonography. Urodynamic studies were carried out to determine bladder outlet obstruction. Receiver operator characteristic curves were generated to compare the accuracy of the different parameters, and the area under the curve of each parameter was calculated. Bladder outlet obstruction index positively correlated with intravesical prostatic protrusion, total prostate volume, transition zone volume, transition zone index, resistive index and prostate-specific antigen. Further, resistive index was only a significant independent variable with intravesical prostatic protrusion. Intravesical prostatic protrusion had the highest area under the curve of 0.790 among all variables, and its cut-off value was 10 mm. The positive predictive value of intravesical prostatic protrusion was 76.2%. In addition, the positive predictive value of the combined parameters intravesical prostatic protrusion and resistive index increased to 83.8%. Intravesical prostatic protrusion and resistive index are useful parameters for predicting bladder outlet obstruction in patients with lower urinary tract symptoms suggestive of benign prostatic hyperplasia. In clinical practice, the combination of intravesical prostatic protrusion and resistive index on ultrasound can be diagnostic of bladder outlet obstruction.