INJ Search


Int Neurourol J > Volume 28(1); 2024 > Article
Kim, Kim, Lee, and Lee: Water Vapor Therapy and Zonal Anatomy of the Prostate


Water vapor therapy using Rezūm has been recently introduced as a minimally invasive surgery for benign prostatic hyperplasia and is being increasingly performed. However, there is a lack of real-time images showing this practice and how convective water vapor acts in the prostate gland. In real-time ultrasonography, convective water vapor rapidly spreads throughout the ipsilateral transitional zone and is mostly limited within the transitional zone. For educational purposes, we would like to present a case to help readers understand water vapor therapy by visualizing convective water vapor using real-time ultrasound.

Although the first paper for Rezum was reported in 2015, there is no real-time image of how the convective water vapor acts in the prostate gland. Very recently, on June 27, 2023, the first water vapor therapy was performed in South Korea. We thought that the visualization using real-time ultrasound during the water vapor therapy could inspire surgeons who wonder how the mechanism really works. We provide here a short video clip and relevant explanations showing real-time ultrasound of convective water vapor during water vapor therapy using Rezum.


A 62-year-old man who was sexually active presented with acute urinary retention. Catheterization and the administration of an alpha-1 antagonist for 3 days facilitated him in voiding by himself. After a month, the patient visited the outpatient clinic to evaluate voiding function. Serum prostate-specific antigen level (ng/mL), prostate size (total/transitional, mL), International Prostate Symptom Score (IPSS) score, maximum urine flow rate (Qmax; mL/sec), and International Index of Erectile Function (IIEF-5) score were 1.10, 40.2/8.6, 15, 9.8, and 15, respectively. He wanted to undergo prostate surgery and desired to maintain his ejaculatory function. We had no choice but to perform water vapor therapy (WVT). During the operation, it was enough for us to deploy the vapor needle into only 2 points (each point at 8 and 4 o’clock on the lateral lobes). At 3 months after the operation, the prostate-specific antigen level (ng/mL), prostate size (total/transitional, mL), IPSS score, Qmax (mL/ sec), and IIEF-5 score were 1.06, 34.1/5.6, 5, 15.1, and 14, respectively. The reduction volumes of the total prostate and transitional zone were 15.2% and 34.8%, respectively, in the present study (Fig. 1). There were no postoperative complications.


According to McVary et al. [1], WVT for benign prostatic hyperplasia (BPH) improved urinary symptoms and the Qmax by approximately 50%, which was maintained over 5 years [1]. Considering that transitional zone growth is the main contributor to BPH progression [2], BPH procedures including WVT should make a therapeutic effect on the transitional zone of the prostate. Now that there was a report indicating that specimens had defects around the prostatic urethra after WVT, which was identified by vital staining [3], we could assume that convective vapor mainly acts in the transitional zone of the prostate. Wong et al. [4] showed that the prostatic urethra was wider than the baseline size in postoperative cystoscopy. However, there has been a lack of real-time images showing WVT, so surgeons may wonder how convective water vapor spreads into the prostate, or surgeons might have a concern for unrecognized complications such as adjacent organ damage. Therefore, visualization of vapor convection may offer readers comprehensive information for the range of convection when WVT is performed.
It was not comfortable for us to apply ultrasound simultaneously during WVT because we had to manipulate a delivery device that was attached to a cystoscope. In fact, surgeons do not have to use intraoperative ultrasonography during WVT. However, by watching a short video clip that we provided, physicians may recognize the approximative boundary of water vapor in the transitional zone and may understand why we keep the injection point 1 cm (approximately 2 fields of view) away from the bladder neck and other injection points [5]. Convective water vapor spreads rapidly to approximately 1 cm from the deployment site and was mostly limited to the transitional zone (Supplementary video clip); however, tiny streams seemed to be delivered into the ipsilateral peripheral zone.


Supplementary Video clip can be found via
Supplementary video clip 1.


Research Ethics
The Institutional Review Board of St. Vincent’s Hospital approved this case study design and access to the patients’ medical records (approval number: VC23ZASI0165, approval date: July 14, 2023). This study was performed in accordance with the Declaration of Helsinki. This article does not reference any animal studies performed by any of the authors. Informed consent was obtained from the participant in the study.
Conflict of Interest
No potential conflict of interest relevant to this article was reported.
· Conceptualization: JHK, DSL
· Data curation: HYK
· Methodology: HYK
· Project administration: SJL
· Writing - original draft: DSL
· Writing - review & editing: JHK


1. McVary KT, Gittelman MC, Goldberg KA, Patel K, Shore ND, Levin RM, et al. Final 5-year outcomes of the multicenter randomized sham-controlled trial of a water vapor thermal therapy for treatment of moderate to severe lower urinary tract symptoms secondary to benign prostatic hyperplasia. J Urol 2021;206:715-24. PMID: 33872051
crossref pmid
2. Cao N, Lu Q, Si J, Wang X, Ni J, Chen L, et al. The characteristics of the transitional zone in prostate growth with age. Urol 2017;105:136-40. PMID: 28389262
crossref pmid
3. Dixon CM, Cedano ER, Mynderse LA, Larson TR. Transurethral convective water vapor as a treatment for lower urinary tract symptomatology due to benign prostatic hyperplasia using the Rezūm® system: evaluation of acute ablative capabilities in the human prostate. Res Rep Urol 2015;7:13-8. PMID: 25674555
pmid pmc
4. Wong A, Mahmalji W. The role of Rezūm™ steam ablation of the prostate in the treatment of patients with acute urinary retention secondary to benign prostatic hyperplasia. A single center, single surgeon case series and literature review. Aging Male 2020;23:1620-6. PMID: 33818292
5. Siena G, Cindolo L, Ferrari G, Maruzzi D, Fasolis G, Condorelli SV, et al. Water vapor therapy (Rezūm) for lower urinary tract symptoms related to benign prostatic hyperplasia: early results from the first Italian multicentric study. World J Urol 2021;39:3875-80. PMID: 33787986
crossref pmid pmc pdf

Fig. 1.
Transrectal ultrasound images of the prostate at baseline (A) and 3 months after water vapor therapy (B). The volume of the transitional zone of the prostate gland was reduced (34.8%) from 8.6 mL to 5.6 mL, and the prostatic urethra seemed to become widened. Yellow line: transi- tional zone.
Share :
Facebook Twitter Linked In Google+
METRICS Graph View
  • 0 Crossref
  • 0 Scopus
  • 1,521 View
  • 64 Download
We recommend

Article Category

Browse all articles >


Browse all articles >


Browse all articles >


Browse all articles >


Official Journal of Korean Continence Society & ESSIC (International Society for the Study of BPS) & Korean Society of Urological Research & The Korean Children’s Continence and Enuresis Society & The Korean Association of Urogenital Tract Infection and Inflammation & Korean Society of Geriatric Urological Care
Editorial Office
Department of Urology, Kangbuk Samsung Medical Center, Sungkyunkwan University School of Medicine,
29 Saemunan-ro, Jongno-gu, Seoul 03181, Korea
Tel: +82-2-2001-2237     Fax: +82-2-2001-2247    E-mail:

Copyright © 2024 by Korean Continence Society.

Developed in M2PI

Close layer
prev next