Dr. Neal Shore

The Science of Steam: Treating BPH Safely, Efficiently and Effectively

Editorial Commentary by Neal D. Shore, MD, FACS
Medical Director, Carolina Urologic Research Center

All BPH Articles / Clinical Studies / The Science of Steam: Treating BPH Safely, Efficiently and Effectively

Dr. Neal Shore has conducted more than 250 clinical trials for urologic conditions and treatments. He serves as the National Urology Research Director for 21st Century Urology, is a member of the American Urological Association’s Data Committee, the SITC Task Force for Prostate Cancer, the Bladder Cancer Advocacy Think Tank, and sits on the editorial boards of several urology publications. He is a Fellow of the American College of Surgeons and is board-certified by the American Board of Urology.

In this article, Dr. Shore shares his knowledge and experience with Rezūm™ Water Vapor Therapy, the science behind steam therapy and how this treatment relieves symptoms caused by an enlarged prostate, or benign prostatic hyperplasia (BPH). 


A clinical study supports that Rezūm Therapy is an efficient, safe, office-based treatment for BPH.1 Rezūm Therapy delivers a uniform distribution of heat to the prostate in the form of water vapor (steam) that results in immediate cell death but doesn’t char tissue, and lesions are contained to the targeted treatment zone without compromising surrounding structures.2,3 Over time, the body’s natural healing response removes the treated tissue, resulting in a decrease in the size of the prostate. A clinical trial showed significant improvement in BPH symptoms through five years – and only 4.4% of patients treated with Rezūm Therapy in the trial required a second surgical treatment to address their BPH symptoms.1 The same clinical study also showed no new reported instances of erectile dysfunction (ED) for patients who received Rezūm Therapy.1 

How it Works

The Rezūm System delivers steam into the targeted prostate tissue in increments of 9 seconds. The transfer of energy is uniform, which increases the predictability of the procedure.2

Watch a demonstration in this video.


In the Rezūm Therapy procedure, when the steam is delivered to the prostate tissue, it condenses into water and releases the stored energy. This is an efficient way to transfer energy inside the body because the vapor is dispersed in the prostate tissue and delivered in a matter of seconds.

The steam is delivered to the prostate at a temperature of about 103°C; it does not break through tissue. Instead, steam travels through cell spaces until it meets a boundary, such as a membrane. On reaching the membrane, steam condenses within the cell spaces back to water releasing the stored energy, bringing the tissue temperature to approximately 70°C-80°C, which leads to immediate cell death.4,5 Upon cell death, the body’s natural processes come into play. Inflammation occurs and the body’s inflammatory system sends out cells that act as scavengers to the swollen area in the prostate.6 The body, with the help of the scavenger cells, resorbs the dead tissue over time and the prostate volume is reduced.7

The number of 9-second injections needed to complete a Rezūm procedure depends on the size and anatomy of the prostate.8 Hence, the Rezūm Therapy procedure may be specifically performed for each patient’s anatomical requirements. On average, 4.5 injections were used to treat men in the Rezūm Therapy clinical trial, and the average procedure time in the trial was less than 10 minutes.


The five-year data from the Rezūm clinical study showed the durability of Rezūm Therapy. Surgical retreatment was low – only 4.4% of patients later needed another surgical procedure for BPH, and 11.1% later needed medications for BPH symptom management following their Rezūm Therapy treatment.1

You can learn more about the five-year Rezūm Therapy clinical study here.


The natural boundaries within the prostate contain the steam from the Rezūm Therapy treatment, preventing the steam from traveling to nearby structures.3 In this way, steam is a safe energy transfer therapy.7

The most common side effects patients experience with Rezūm Therapy are mild to moderate, last only a short time and typically go away within a few weeks.* These include painful or frequent urination, blood in the urine or semen, decrease in ejaculatory volume, urinary tract infection, inability to urinate or completely empty the bladder, and an urgent need to urinate.* In the Rezūm Therapy clinical trial, there were no reports of new instances of erectile dysfunction (ED) through the duration of the study (five years).1

Note: For a complete list of risks and to understand these potential side effects, visit the Rezūm Therapy risks page.


Clinical studies support that Rezūm Therapy relieves BPH symptoms safely and effectively. Steam is efficient, needing only 9 seconds per injection and resulting in immediate cell death. After the immune system scavenges the area of dead cells, the prostate gland volume shrinks. Rezūm Therapy demonstrated significant improvement in BPH symptoms. These improvements have been sustained through five-year follow-up, with a best-in-class surgical retreatment rate of only 4.4% for returning BPH symptoms.1

*Patient responses can and do vary.  

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  1. McVary KT, Gittelman MC, Goldberg KA, et al. Final 5-year outcomes of the multicenter randomized sham-controlled trial of Rezūm water vapor thermal therapy for treatment of moderate-to-severe lower urinary tract symptoms secondary to benign prostatic hyperplasia. J Urol. 2021 Sep;206(3):715-24.
  2. Data on file with Boston Scientific. Michael Hoey, Water vapor for tissue ablation, March 7, 2009
  3. Mynderse LA, Hanson D, Robb RA, et al. Rezūm System water vapor treatment for lower urinary tract symptoms/benign prostatic hyperplasia: validation of convective thermal energy transfer and characterization with magnetic resonance imaging and 3-dimensional renderings. Urology. 2015 Jul;86(1):122-7.
  4. Westwood J, Geraghty R, Jones P, et al. Rezūm: a new transurethral water vapour therapy for benign prostatic hyperplasia. Ther Adv Urol. 2018 Nov;10(11):327-33.
  5. Woo HH, Gonzalez RR. Perspective on the Rezūm® System: a minimally invasive treatment strategy for benign prostatic hyperplasia using convective radiofrequency water vapor thermal therapy. Med Devices (Auckl). 2017;10:71-80.
  6. Rock KL, Kono H. The inflammatory response to cell death. Annu Rev Pathol. 2008;3:99-126.
  7. Das AK, Leong JY, Roehrborn CG. Office-based therapies for benign prostatic hyperplasia: a review and update. Can J Urol. 2019 Aug;26(Suppl 1):2-7. 
  8. Roehrborn CG, Gange SN, Gittelman MC, et al. Convective thermal therapy: Durable 2-year results of randomized controlled and prospective crossover studies for treatment of lower urinary tract symptoms due to benign prostatic hyperplasia. J Urol. 2017 Jun;197(6):1507-16.

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Content on this web page is for Informational Purposes only and does not constitute medical advice and should not be used for medical diagnoses. Boston Scientific strongly recommends that you consult with your physician on all matters pertaining to your health or to address any clinical/medical questions.
IMPORTANT INFORMATION: These materials are intended to describe common clinical considerations and procedural steps for the use of referenced technologies but may not be appropriate for every patient or case. Decisions surrounding patient care depend on the physician’s professional judgment in consideration of all available information for the individual case.
Boston Scientific (BSC) does not promote or encourage the use of its devices outside their approved labeling. Case studies are not necessarily representative of clinical outcomes in all cases as individual results may vary.
Results from case studies are not necessarily predictive of results in other cases. Results in other cases may vary. 
Neal D. Shore, MD, is a Boston Scientific consultant and was compensated for his contribution to this article. All images are the property of Boston Scientific. All trademarks are the property of their respective owners.
Rezum.com is a website sponsored by Boston Scientific.