Resistive Index of Prostate Capsular Arteries: A Newly Identified Parameter to Diagnose and Assess Bladder Outlet Obstruction in Patients with Benign Prostatic Hyperplasia

Purpose: We evaluated the association of the resistive index of the prostate capsular arteries and bladder outlet obstruction severity in men with benign prostatic hyperplasia. Materials and Methods: A total of 74 patients histologically diagnosed with benign prostatic hyperplasia were ultimately enrolled in this prospective study. Urodynamics were performed by a urologist to determine bladder outlet obstruction. Baseline parameters measured in patients with benign prostatic hyperplasia were the prostate capsular artery resistive index, International Prostate Symptom Score, quality of life score, total prostate and transition zone volume, and the transition zone index. ROC curves were produced to calculate the ROC AUC and evaluate the diagnostic performance of the prostate capsular artery resistive index, International Prostate Symptom Score, obstructive symptoms, total prostate and transition zone volume, and the transition zone index for bladder outlet obstruction. Results: Significant difference between patients with and without bladder outlet obstruction was observed in the resistive index, which showed the highest coefficient with the degree of obstruction (r = 0.712, p <0.0001). At a cutoff of 0.69 the resistive index distinguished patients with and without bladder outlet obstruction with 78% sensitivity and 86.4% specificity. The prostate capsular artery resistive index had the maximum AUC of 0.823. Conclusions: The prostate capsular artery resistive index is significantly higher in patients with benign prostatic hyperplasia related bladder outlet obstruction than in those without such obstruction. The resistive index might serve as a novel indicator to diagnose and assess bladder outlet obstruction in patients with benign prostatic hyperplasia.