To assess the potential factors influencing the occurrence of bladder outlet obstruction (BOO) during follow-up after high-intensity focused ultrasound (HIFU) treatment for localized prostate cancer.

Patients treated with HIFU who had a minimal follow-up of 1 year were included in this retrospective analysis. BOO was classified as bladder neck, necrosis of the prostate, distal stenosis, urethral stenosis, and single and repetitive BOO. We analyzed the risk group (American Joint Commission on Cancer), age, prostate volume before HIFU, treated prostate volume on HIFU, pre-HIFU transurethral resection of the prostate (TURP), ratio of resected volume/initial prostate volume by TURP before HIFU, and interval between TURP and HIFU. P values of less than 0.05 were considered statistically significant.

The mean follow-up of the 315 patients analyzed was 40 ± 19 months (range 12 to 109). BOO developed in 79 patients (25.1%), with 19 experiencing multiple BOO episodes. The mean interval to the first development of BOO was 15.2 ± 19.3 months. The distribution of a single episode of BOO for the etiologies of bladder neck, necrosis of the prostate, distal stenosis, and urethral stenosis was 64 (81%), 24 (30.4%), 13 (16.5%), and 10 (12.7%), respectively. Older age at HIFU was the only factor significantly associated with the development of BOO (P = 0.021). In those with multiple BOO episodes, the main type of obstruction was at the bladder neck. The rate of multiple BOO episodes was significantly lower with a greater volume of resected tissue by TURP before HIFU (P = 0.031).

The results of our study have shown that the development of BOO after HIFU is associated with older age. TURP before HIFU was not an independent factor in the prevention of BOO during follow-up, but multiple BOO episodes were reduced by resecting more tissue at TURP before HIFU.