Which is a better indicator of bladder outlet obstruction in patients with benign prostatic enlargement--intravesical protrusion of prostate or bladder wall thickness?

OBJECTIVE To determine the correlation of intravesical prostatic protrusion (IPP) and bladder wall thickness (BWT) with clinical and urodynamic parameters, as well as their sensitivity and specificity with regard to bladder outlet obstruction in patients with a benign prostatic enlargement (BPE). MATERIALS AND METHODS 111 patients with lower urinary tract symptoms and confirmed BPE completed the International Prostatic Symptom Score (I-PSS), as well as a transabdominal ultrasound to determine their prostate volume, a grade of IPP and BWT. All the patients were then subjected to the complete urodynamic studies (UDS). RESULTS The IPP showed a good correlation with the prostate volume (r = 0.61) and serum PSA (r = 0.48); p = 0.0000, free uroflowmetry (r = -0.27; p = 0.004), as well as the determinants of urodynamic obstruction: bladder outlet obstruction index-BOOI (r = 0.36; p < 0.0001), and ICS and Schaefer obstruction class nomograms (rho = 0.33 and rho = 0.39, respectively; p < 0.001), while the BWT showed only a statistical correlation with age (r = 0.23; p = 0.02) and serum PSA (r = 0.4; p = 0.0000), regardless of an significant correlation with the IPP (r = 0.45; p = 0.0000). The ANOVA test showed a significant difference between the IPP grades for the observed clinical and urodynamic variables with an increase in significance for IPP>10 mm. The area under the ROC curve in the prediction of obstruction for the IPP is 0.71 (sensitivity 59.6, specificity 81.4), while the AUC for the BWT is 0.61 (sensitivity 64.5, specificity 59.2). The stepwise logistic regression model shows that most significant independent variables for the obstruction are the IPP, Q(max) free and age, with the area under the ROC curve of 0.78 (95% CI 0.695 to 0.856). CONCLUSION The IPP higher than 10 mm as a non-invasive predictor of infravesical obstruction shows good correlations with clinical and urodynamic parameters, while the specificity and PPV against obstruction are significant. Despite a good correlation with IPP, the BWT is only a modest indicator of obstruction.