Benign prostatic enlargement (BPE) is a non-malignant growth of the prostate gland that can lead to a range of lower urinary tract symptoms (LUTS), and in some cases eventually leading to retention of urine. In patients failing to wean off catheter after retention of urine due to BPE, surgical intervention is the standard treatment.

Surgical intervention options have evolved from electrosurgical resection to the use of lasers for enucleation and ablation \[1\]. Transurethral resection of prostate (TURP) was first performed over 80 years ago and is still regarded as the "gold standard" for the treatment of BPE in prostates between 30 and 80ml \[2\]. While TURP results in a statistically significant improvement in symptoms score and and maximum urinary flow rate (Qmax), perioperative morbidity and long-term complications can include postoperative bleeding, urinary retention, incontinence, urethral strictures, erectile dysfunction, and ejaculatory dysfunction \[3\].

Rezum system use the principle of thermodynamic principle of convective energy transfer, which is different to other conductive heat transfer techniques like transurethral microwave therapy or transurethral needle ablation. \[4\] In the Rezum system, radiofrequency power is used to create thermal energy in the form of water vapor, which in turn deposits the stored thermal energy during the change from steam phase to liquid after injected into the prostatic tissue. The Rezum system contained a generator with a radiofrequency power supply to create water vapor from sterile water and a single-use transurethral delivery device. The tip of the delivery device contains an 18-gauge needle where 12 small emitter holes spaced circumferentially for dispersion of water vapor into the targeted prostatic tissue. The injection is at a pressure slightly higher than interstitial pressure. Due to the convective properties of water vapor, the injected steam will disperse rapidly and homogenously through the tissue and releases stored thermal energy into prostatic tissue. The released thermal energy will cause tissue necrosis. The most important character of the treatment is when the transition zone is treated, its energy will only deposit within the zonal anatomy of the prostate. Studies by histologic and MRI imaging had shown that after treatment, the thermal lesions were only limited to the transition zone without extension to the peripheral zone, bladder, rectum or striated urinary sphincter \[5,6\]. It was shown that 6 mo after treatment the total prostate volume was reduced by 28.9% and the resolution of thermal lesions as determined with Gadolini- um-enhanced magnetic resonance imaging was almost complete. \[6\] A small pilot study had shown that Rezum could provide safe and effective treatment upto one year for men with LUTS due to BPE. \[7\] In the first multicentre, randomised, controlled study 197 men were enrolled and randomised in a 2:1 ratio to treatment with the Rezum system or control. \[8\] The sham procedure (control) was rigid cystoscopy with imitated treatment sounds. The primary efficacy end point was met at 3 months with relief of symptoms measured by a change in International prostate symptom score (IPSS) of 50% for the treatment arm compared to 20% for the control group (p \< 0.0001). In the thermal treatment arm, the maximal uroflow rate increased significantly by 67% from 9.9 ml/s to 16.1 ml/s (p \< 0.0001) after 3 months. The clinical beneficial outcome was sustained throughout the study period with an improvement of 54% at the 12-mo follow up. In the latest updated report on the 4-year outcome, the improvement in voiding (as measured by IPSS and uroflowmetry) was sustained to 4 years with surgical retreatment rate of only 4.4%. \[9\] Therefore, Rezum was proven to be an effective treatment for BPH.

However, all studies focused on the application of Rezum in patients with LUTS are from Caucasian population. Therefore, in this study, investigator plan to evaluate the feasibility and safety of Rezum in the management of Chinese male patients with LUTS secondary to BPE. This could provide information on the tolerability and effectiveness of the treatment in local population.