Ultrasound assessment of intravesical prostatic protrusion and detrusor wall thickness--new standards for noninvasive bladder outlet obstruction diagnosis?

PURPOSE We evaluated the accuracy of detrusor wall thickness and intravesical prostatic protrusion, and the association of each test to diagnose bladder prostatic obstruction in patients with lower urinary tract symptoms. MATERIALS AND METHODS We enrolled in the study 100 consecutive patients with lower urinary tract symptoms due to benign prostatic hyperplasia. Baseline parameters were International Prostate Symptom Score, prostate volume, urinary flow rate, intravesical prostatic protrusion, detrusor wall thickness, Schaefer obstruction class, minimal urethral opening pressure and the urethral resistance algorithm bladder outlet obstruction index. A ROC curve was produced to calculate AUC and evaluate the diagnostic performance of intravesical prostatic protrusion, detrusor wall thickness and prostate volume for bladder prostatic obstruction. RESULTS We noted a highly significant correlation between intravesical prostatic protrusion and the bladder outlet obstruction index (Spearman's rho = 0.49, p = 0.001), and Schaefer obstruction class (Spearman's rho = 0.51, p = 0.001). A highly significant correlation was also observed for detrusor wall thickness and the bladder outlet obstruction index (Spearman's rho = 0.57, p = 0.001), detrusor wall thickness and Schaefer obstruction class (Spearman's rho = 0.432, p = 0.02). On multivariate analysis intravesical prostatic protrusion and detrusor wall thickness were the only parameters associated with bladder prostatic obstruction (p = 0.015). The AUC for intravesical prostatic protrusion was 0.835 (95% CI 0.756-0.915) and for detrusor wall thickness it was 0.845 (95% CI 0.78-0.91). The association of intravesical prostatic protrusion and detrusor wall thickness produced the best diagnostic accuracy (87%) when the 2 tests were done consecutively. CONCLUSIONS Suprapubic ultrasound of detrusor wall thickness and intravesical prostatic protrusion is a simple, noninvasive, accurate system to assess bladder prostatic obstruction in patients with lower urinary tract symptoms due to benign prostatic hyperplasia.