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

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.

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.

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 (Qmax; 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 H2O) from preoperatively 70 +/- 23 (mean +/- SD) to 51 +/- 22 (p < 0.005) postoperatively and a decline of the detrusor pressure at maximum flow (cm H2O) from 74.2 +/- 24 to 57 +/- 15 (p < 0.005). The linear passive urethral resistance relations (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 preoperatively as obstructed, the remaining 20% as being in equivocal zone. Postoperatively, 13% were obstructed, 50% in the equivocal zone and 37% of patients were rated as obstructed.

Transrectal HIFU is capable of improving objective and subjective BPH parameters as well as of decreasing the degree of bladder outflow obstruction.