The urodynamic impact of transrectal high-intensity focused ultrasound on bladder outflow obstruction

Objectives : The aim of this study was to determine the urodynamic impact of transrectal high-intensity focused ultrasound (HIFU), which is presently evaluated as a minimally invasive treatment option for benign prostatic hyperplasia (BPH), on bladder outflow obstruction by means of pressure flow analyses. Methods : A total number of 30 patients suffering from symptomatic BPH underwent pressure flow studies before and after transrectal HIFU (mean time interval : 4.5 months ; range : 3-6 months). In parallel, the international prostate symptom score (IPSS), free flow and postvoid residual volume were determined at regular time intervals postoperatively. Results : The IPSS decreased from preoperatively 15.8 ± 5.9 (n = 30 ; mean ± SD) to 6.9 ± 4.4 at 3 months (n = 30) and 7.2 ± 5 at 6 months (n = 30). Within the same time period the maximum uroflow (Q max ; ml/s) increased from 8.8 ± 2.2 to 11.3 ± 3.4 (3 months) and 12.1 ± 3.6 (6 months) and the postvoid residual volume (ml) declined from 100 ± 47 to 44 ± 33 and 55 ± 50, respectively. Pressure flow studies revealed a reduction of the minimal voiding pressure (cm H 2 O) from preoperatively 70 ± 23 (mean ± SD) to 51 ± 22 (p < 0.005) postoperatively and a decline of the detrusor pressure at maximum flow (cm H 2 O) from 74.2 ± 24 to 57 ± 15 (p < 0.005). The linear passive urethral resistance relation (linear PURR) dropped from 3.7 ± 1.1 to 2.2 ± 1.2 (p < 0.005). According to the Abrams-Griffiths nomogram, 24 (80%) patients were classified pre-operatively as obstructed, the remaining 20% as being in equivocal zone. Postoperatively, 13% were unobstructed, 50% in the equivocal zone and 37% of patients were rated as obstructed. Conclusion : Transrectal HIFU is capable of improving objective and subjective BPH parameters as well as of decreasing the degree of bladder outflow obstruction.