Evidence Notes · No. 02
← All notesA robotically executed waterjet, planned on live ultrasound, that removes substantial tissue while usually leaving ejaculation intact. Five years of evidence — and not yet more than that.
Aquablation is one of the newer surgical treatments for an enlarged prostate, or benign prostatic hyperplasia (BPH). It uses ultrasound imaging and a robotically controlled high-pressure water jet to remove prostate tissue that is blocking the flow of urine.
What makes Aquablation particularly interesting is the balance it attempts to achieve: substantial relief of urinary obstruction while reducing the likelihood of losing normal ejaculation.
The evidence base has developed considerably. Aquablation has now been studied in randomised controlled trials, systematic reviews, prospective international studies and large real-world datasets. Five-year results are available for prostates up to 150 mL.
However, Aquablation is still an operation. Bleeding remains an important consideration, ejaculation cannot be guaranteed, and evidence beyond five years remains much less mature than for longstanding procedures such as TURP and HoLEP.
So what does the research actually tell us?
Aquablation is an operation used to treat urinary obstruction caused by an enlarged prostate.
The prostate sits underneath the bladder and surrounds the urethra, the tube through which urine leaves the bladder.
As the inner part of the prostate enlarges, it can compress the urethra and cause symptoms such as:
Aquablation removes some of the prostate tissue causing this obstruction.
There are no external surgical cuts: the treatment is performed through the urethra.
Aquablation combines:
An ultrasound probe provides the surgeon with a live image of the prostate.
The surgeon then maps out which areas of prostate should be removed and which structures should be protected. Particular attention can be paid to tissue around structures involved in ejaculation.
Once the treatment plan has been confirmed, the AquaBeam system directs a high-velocity jet of saline through the prostate.
The robot executes the planned resection, but the surgeon remains responsible for planning and controlling the operation.
The water jet itself removes tissue without using heat. However, this does not mean the entire operation is completely “heat-free”. Electrical cautery may subsequently be used to seal bleeding vessels.
The evidence indicates that Aquablation produces a substantial improvement in urinary symptoms for most appropriately selected patients.
One of the most useful recent analyses combined 528 men from five prospective international studies.
Average International Prostate Symptom Score (IPSS) fell from:
21.5 before treatment → 5.8 at six months → 6.6 at 12 months.
Maximum urinary flow rate, known as Qmax, increased from:
8.1 mL/second before treatment → 19.0 mL/second at three months → 20.5 mL/second at 12 months.
The average amount of urine remaining in the bladder after urination fell from:
106 mL → 53 mL at 12 months.
These figures suggest a large average improvement in both symptoms and urinary flow.1
The International Prostate Symptom Score is a questionnaire commonly used to measure urinary symptoms.
It asks about:
The total score ranges from 0 to 35:
So a reduction from approximately 21–23 before treatment to around 6–7 afterwards represents a substantial average improvement.
A systematic review and meta-analysis of seven studies involving 551 patients found an average IPSS improvement of approximately 16.5 points by three months, with the benefit maintained through 12 months.
However, the authors also found considerable variation between some of the included studies. Therefore, 16 points should be viewed as an average rather than a prediction for every patient.2
Symptom score (IPSS)
21.5→6.6of 35, at 12 months
528 men pooled from five prospective international studies.
Peak urinary flow
8.1→20.5mL/second
Same pooled analysis, at 12 months.
Urine left behind
106→53mL
Halved by 12 months — the bladder emptying properly again is often what men notice first.
Urinary flow commonly improves markedly after Aquablation.
In the pooled analysis described above:
Qmax increased from 8.1 to 20.5 mL/second at 12 months.1
In the WATER II study of larger prostates, Qmax increased from:
8.6 → 17.1 mL/second at five years.3
The randomised WATER trial also showed sustained improvement in urinary flow five years after surgery.
Peak urinary flow had increased by approximately:
It is important to remember that urinary flow depends on the bladder as well as the prostate.
Someone whose bladder muscle has become weak after years of obstruction may not achieve the same urinary flow as someone whose bladder remains strong, even if the prostate obstruction has been successfully removed.
Aquablation physically removes prostate tissue during the operation rather than relying on the prostate gradually shrinking over several months.
Substantial improvement is therefore seen relatively quickly.
In the prospective WATER II study of men with prostates between 80 and 150 mL, average IPSS fell from:
23.2 before surgery → 6.7 by three months.
Maximum urinary flow increased from:
8.7 → 18.8 mL/second by six months.
Residual urine fell from:
131 → 47 mL.5
However, removal of the obstruction is not the same as complete recovery.
During the early healing period, patients may still experience:
The bladder may also need time to adjust after having worked against an obstruction for many years.
Aquablation now has good five-year evidence.
That is important because early criticism of the procedure centred partly on the relatively short follow-up available for a new technology.
The WATER study randomly assigned men to Aquablation or TURP and followed them for five years.
At five years, IPSS had improved by:
The difference was not statistically significant overall, meaning both treatments remained highly effective.4
WATER II prospectively followed 101 men with much larger prostates.
Average prostate volume was 107 mL.
At five years:
IPSS: 22.6 → 6.8
Qmax: 8.6 → 17.1 mL/second
and approximately:
96.3% of patients remained free from another BPH procedure.3
A subsequent five-year analysis comparing the WATER and WATER II populations produced remarkably similar results despite their very different prostate sizes.
For prostates measuring 30–80 mL:
IPSS: 22.9 → 7.0
Qmax: 9.4 → 17.3 mL/second
For prostates measuring 80–150 mL:
IPSS: 23.2 → 6.8
Qmax: 8.7 → 17.1 mL/second.
At five years:
remained free from surgical retreatment.6
These are reassuring results.
However, five-year durability should not be confused with lifetime durability.
HoLEP and TURP have much longer follow-up extending beyond ten years.
Aquablation does not yet have an equivalent body of 10–20-year evidence.
Free from another BPH operation
95%at 5 years · 30–80 mL
WATER, the randomised trial against TURP.
Free from another BPH operation
97%at 5 years · 80–150 mL
WATER II, prospective, 101 men, average gland 107 mL.
Five years is not a lifetime These are genuinely reassuring numbers for a newer technology. They are not the same thing as the ten- and twenty-year record TURP and HoLEP have, and it is worth being clear about which of those you are being offered.
The answer depends partly on what researchers mean by “retreatment”.
Some studies count only another operation.
Others include restarting BPH medication.
For patients, surgical retreatment is probably the clearest measure.
At five years:
remained free from another BPH operation.
That translates approximately into surgical retreatment rates of:
respectively.6
In WATER II specifically, freedom from a secondary BPH procedure was 96.3% at five years.3
The randomised WATER trial also found that the risk of requiring additional BPH treatment — defined more broadly as medication or surgery — was lower after Aquablation than after TURP over five years.4
Overall, the evidence therefore supports a relatively low five-year retreatment rate, but retreatment is not zero and longer follow-up remains necessary.
Aquablation should not be confused with a minor office procedure.
It removes a significant amount of prostate tissue and is carried out under a general anaesthetic.
Potential complications include:
A 2025 systematic review examining 47 studies found that most reported complications were minor — Clavien–Dindo grade 1 or 2 — while severe complications were less common.
Bleeding remained the main perioperative concern.
Across the included studies, blood transfusion was required in approximately 1–8%, with higher rates generally seen in larger prostates and in some of the earlier Aquablation series.
Long-term complications such as urethral stricture or bladder-neck narrowing were uncommon.7
The wide range of reported complication rates is important. Studies have used different prostate sizes, surgical techniques and definitions of complications, so a single percentage cannot accurately describe every patient’s risk.
Bleeding is probably the most important safety issue to understand when considering Aquablation.
The evidence has also changed substantially as the technique has evolved.
In the original WATER II study involving prostates of 80–150 mL, bleeding was relatively prominent.
The early six-month study reported bleeding requiring an intervention and/or transfusion in 14 of 101 patients.
This was early experience with large prostates, and haemostasis — the technique used to control bleeding — has subsequently changed considerably.5
More recent evidence suggests lower bleeding rates.
In the 2026 international ICARUS real-world study, 1,946 men undergoing Aquablation were compared with the original WATER populations.
Among men with prostates between 80 and 150 mL, transfusion was required in:
1.3% in contemporary real-world practice
compared with:
5.9% in the original WATER II population.8
This suggests that improvements in surgical technique, haemostasis and experience may have reduced bleeding risk.
Another large real-world analysis examined 70,270 Aquablation procedures performed between 2019 and 2024 and reported a combined rate of transfusion or return to theatre for bleeding of approximately 0.2%.
However, this figure requires particular caution. The analysis incorporated a corporate database, manufacturer procedure counts and adverse-event surveillance data. Such databases can underestimate complications compared with carefully monitored prospective clinical trials.
It is therefore useful evidence that serious bleeding appears uncommon in contemporary practice, but the 0.2% figure should not be treated as the definitive personal risk for an individual patient.9
A reasonable overall interpretation is that bleeding remains an important potential complication, particularly with large prostates, but contemporary rates appear lower than those reported during the early development of Aquablation.
Transfusion, 80–150 mL glands
5.9%→1.3%early trial → contemporary practice
WATER II versus the 2026 ICARUS real-world series of 1,946 men.
Why I am not quoting you 0.2% A 70,270-procedure analysis reports that figure for transfusion or return to theatre. It draws on a corporate database and adverse-event surveillance, both of which undercount compared with monitored trials. It is evidence that serious bleeding is uncommon — not your personal risk.
The available evidence is generally reassuring.
Aquablation has not been shown to cause a major deterioration in erectile function in most men.
A systematic review published online in 2025 and in the 2026 journal issue included 15 studies and 1,533 patients. Erectile function remained stable across the included Aquablation studies.10
Earlier reviews reached similar conclusions, although the amount of high-quality randomised evidence specifically examining erections was smaller than the evidence for urinary outcomes.
This means the most appropriate conclusion is:
There is no convincing evidence that Aquablation commonly causes erectile dysfunction, but the erectile-function evidence is less extensive than the urinary symptom evidence.
This is where Aquablation differs most clearly from traditional prostate operations.
Conventional TURP and HoLEP frequently result in loss of normal forward ejaculation.
Aquablation was designed to allow the surgeon to map the treatment in a way that avoids some of the tissue important for ejaculation.
The systematic review described above included 15 studies involving 1,533 patients.
Reported preservation of forward — or antegrade — ejaculation ranged from:
72% to 99.6%.
Erectile function remained stable.10
The wide range illustrates an important point: ejaculation preservation is likely, not guaranteed.
Results depend on:
The strongest evidence comes from the randomised WATER trial comparing Aquablation directly with TURP.
Procedure-related ejaculatory dysfunction occurred in:
7% after Aquablation
compared with:
25% after TURP.4
An analysis of sexually active men with larger prostates found postoperative loss of ejaculation in:
2% after Aquablation
compared with:
41% after TURP.
This was a subgroup analysis rather than the trial’s overall primary outcome and should therefore be interpreted more cautiously.11
Overall, however, the evidence that Aquablation preserves ejaculation more often than TURP is relatively convincing.
The difference may be even greater when Aquablation is compared with conventional HoLEP, although the evidence here is weaker because most direct studies have not been randomised.
A 2025 prospective multicentre study compared 75 Aquablation patients with 75 HoLEP patients.
At six months, both treatments produced substantial improvements.
There was no statistically significant difference in:
IPSS
or in:
Qmax
However, ejaculatory dysfunction was reported in:
89.3% after HoLEP
versus:
6.6% after Aquablation.12
Because this was not a randomised trial and follow-up was only six months, these percentages should not be assumed to apply universally.
Nevertheless, other comparative observational studies have also found substantially better ejaculation preservation after Aquablation.
Ejaculatory dysfunction at six months: 6.6% after Aquablation, 89.3% after HoLEP. One study, 150 men, not randomised — but the direction is not in doubt.
Yes, generally.
In the same prospective comparison, postoperative prostate volume was approximately:
18 mL after HoLEP
versus:
47 mL after Aquablation.
PSA levels also fell more after HoLEP.
This is consistent with the fundamental difference between the two procedures.
HoLEP aims to anatomically enucleate — or shell out — most of the enlarged internal prostate tissue.
Aquablation uses selective image-guided tissue removal and deliberately allows some tissue to be preserved where appropriate.
That may help explain both:
The same study also found a larger average fall in haemoglobin after Aquablation, although transfusion rates were identical at 1.3% in each group.12
The answer depends on the strength of evidence rather than simply on what has technically been performed.
This is the prostate-size range studied in the randomised WATER trial.
Aquablation and TURP produced similar durable urinary improvement at five years, with better preservation of ejaculation after Aquablation.4
WATER II specifically studied prostates in this range.
At five years:
This makes Aquablation unusual among ejaculation-preserving treatments because there is meaningful prospective evidence in relatively large prostates.
Aquablation is increasingly being used for prostates larger than 150 mL.
The pooled prospective analysis included prostates ranging from 20 to 242 mL, while very large real-world datasets contain substantially larger glands.1, 9
However, this does not mean that the evidence is equally strong at every prostate size.
The most mature prospective five-year clinical evidence extends to approximately 150 mL.
Beyond that, evidence is increasingly observational.
For very large prostates, established size-independent procedures such as HoLEP therefore remain particularly important alternatives to discuss.
A median lobe is prostate tissue that grows upwards into the bladder and can sometimes make certain BPH procedures technically more difficult.
Aquablation appears to cope well with this anatomy.
An individual-patient-data meta-analysis combined 425 men from four prospective Aquablation studies.
Prostates ranged from 20 to 150 mL.
Substantial improvements occurred regardless of whether patients had:
Only 0.7% required surgical retreatment for recurrent BPH symptoms during one-year follow-up.13
The evidence therefore suggests that a median lobe is not, by itself, a reason to exclude Aquablation.
This is the most scientifically robust comparison because we have a double-blind randomised controlled trial.
In the WATER trial involving 181 men, urinary symptom improvement at six months was:
Aquablation met the trial’s predefined criterion for non-inferiority — meaning it was sufficiently close to TURP in effectiveness to meet the statistical standard established before the trial began.
At five years:
The difference was not statistically significant.4
The principal difference was ejaculation:
The early composite safety outcome also favoured Aquablation:
However, this was a composite endpoint including persistent minor complications as well as more significant complications, so it should not be interpreted as meaning that 26% of Aquablation patients experienced serious harm.4
Overall:
Aquablation produces urinary results broadly comparable with TURP while preserving ejaculation considerably more often.
This comparison is more complex.
Both treatments produce substantial relief of obstruction.
The prospective comparison described earlier found similar six-month symptom outcomes, while HoLEP produced greater prostate-volume and PSA reduction and Aquablation preserved ejaculation considerably better.12
A separate 2025 propensity-matched observational study of 34 matched patient pairs reached a similar conclusion: symptom improvement was comparable, HoLEP produced greater improvement in Qmax and PSA, and Aquablation preserved ejaculation significantly better.14
A 2026 review of Aquablation versus anatomical endoscopic enucleation concluded that enucleation continues to have the stronger long-term durability record, while Aquablation offers greater ejaculation preservation and greater procedural standardisation.
The review estimated approximately:
This is therefore best understood as a trade-off rather than a contest with one universal winner.
Choose Aquablation for
The cost: bleeding is the main perioperative concern, and there is no ten-year record yet.
Choose HoLEP for
The cost: loss of forward ejaculation in the large majority.
The evidence here is less reliable because many comparisons are indirect.
A systematic review and meta-analysis found significant improvement after:
Aquablation produced larger average improvements in IPSS, quality of life and Qmax.
However, bleeding complications were more prominent with Aquablation.16
A network meta-analysis restricted to randomised studies similarly found that the tissue-removing procedures — Aquablation and TURP — generally produced greater urinary improvements than UroLift and Rezūm.17
But these were largely comparisons between different trials rather than direct head-to-head randomisation, so they are less reliable than WATER’s direct comparison between Aquablation and TURP.
The practical distinction is nevertheless useful.
Aquablation is a more substantial tissue-removing operation and generally produces greater relief of obstruction.
Rezūm and UroLift are less invasive and may involve easier recovery and excellent sexual-function preservation, but usually remove or displace less prostate tissue.
The terminology can be misleading.
Aquablation is minimally invasive in the sense that:
But it is still a significant prostate operation.
It involves:
It is therefore better thought of as an image-guided, robotically executed transurethral prostate operation than as a simple outpatient treatment.
Aquablation may be particularly worth considering when a man has:
It may be particularly attractive to sexually active men looking for greater de-obstruction than many less invasive BPH treatments while accepting somewhat less long-term evidence than HoLEP.
Another treatment may be preferable when:
For some patients this may favour HoLEP.
For others it may favour TURP, Rezūm, UroLift, GreenLight laser, prostatic artery embolisation or another treatment.
The most appropriate procedure depends on what the individual patient values most.
The answer differs depending on the question.
There is evidence from: An IPSS improvement of approximately 15–17 points is repeatedly reported.1, 2, 4
Urinary flow commonly approximately doubles, and substantial improvement is maintained to five years.1, 3, 4
The WATER study provides double-blind randomised evidence extending to five years. Aquablation produces broadly comparable urinary outcomes with better preservation of ejaculation.4
There are prospective multicentre data extending to five years. The major limitation is that WATER II did not randomise patients against HoLEP or simple prostatectomy.3
Real-world experience is increasingly extensive, but high-quality long-term prospective evidence is much more limited.1, 9
A systematic review of 15 studies and 1,533 men reported preservation of forward ejaculation in 72–99.6%. The WATER randomised trial also demonstrated significantly less ejaculatory dysfunction than TURP.10, 4
Systematic reviews have generally found stable erectile function, but erectile outcomes have been studied less extensively than urinary symptoms.10
The systematic evidence confirms that bleeding is the principal perioperative concern. However, contemporary real-world studies report substantially lower transfusion rates than early large-prostate trials, suggesting that haemostasis and surgical experience have improved. The precise modern risk remains difficult to define because studies use different methods of recording complications.5, 7, 8, 9
Several contemporary prospective and propensity-matched studies exist. However, mature long-term randomised head-to-head evidence remains much less extensive than the evidence comparing Aquablation with TURP.12, 14, 15
This remains one of the most important unanswered questions. Aquablation now has convincing five-year results. It does not yet have the 10–20-year evidence base available for established operations such as TURP and HoLEP.
Read the grades this way They describe how confident the literature allows anyone to be about a claim — not how likely the treatment is to work for you.
Aquablation is no longer simply a promising new technology. It now has a meaningful scientific evidence base, including randomised controlled trials, systematic reviews and prospective five-year follow-up.
For appropriately selected men, the evidence suggests that it can produce a large and relatively rapid improvement in urinary symptoms and urinary flow.
Across prospective studies, average IPSS typically falls from the low 20s before surgery to approximately 6–7 following treatment, while urinary flow often approximately doubles.1, 3, 6
The improvements also appear durable to five years.
For prostates measuring 80–150 mL, WATER II found:
IPSS: 22.6 → 6.8
Qmax: 8.6 → 17.1 mL/second
with approximately:
96% remaining free from another BPH operation at five years.3
The strongest comparative evidence comes from the randomised WATER trial.
At five years, symptom relief remained similar to TURP, but procedure-related ejaculatory dysfunction occurred in:
7% after Aquablation versus 25% after TURP.4
More recent comparative studies suggest an even larger ejaculation advantage over conventional HoLEP, although these studies are mainly non-randomised and short-term and should therefore be interpreted cautiously.12, 14
Bleeding remains an important consideration. Early large-prostate studies reported relatively significant bleeding, while contemporary real-world series suggest that this risk has fallen substantially as haemostasis techniques and experience have improved.5, 8, 9
The principal remaining uncertainty is very long-term durability.
Five-year results are reassuring, but Aquablation does not yet have the decades of follow-up available for TURP or the extensive 10-year-plus durability evidence available for HoLEP.
The most useful question for a patient is therefore not simply:
“Is Aquablation better than HoLEP, TURP or Rezūm?”
There is no single answer for every patient.
A more useful question is:
“Which treatment gives me the balance I want between symptom relief, urinary flow, durability, surgical risk, recovery and preservation of ejaculation?”
For a man seeking substantial surgical relief of prostate obstruction while placing a high value on preserving forward ejaculation, Aquablation has one of the strongest evidence profiles among contemporary tissue-removing BPH treatments.
For someone whose overriding priority is maximum tissue removal and the longest-established durability, an anatomical enucleation procedure such as HoLEP may represent a different and potentially preferable balance.
And for someone prioritising the least invasive treatment and quickest procedural recovery, options such as Rezūm or UroLift may offer another set of compromises.
The final decision should therefore consider:
Aquablation’s most distinctive evidence-based advantage is the combination of substantial relief of obstruction with a comparatively high probability of preserving ejaculation. Its main limitations are bleeding risk and the fact that very long-term durability beyond five years is still being established.
Every figure on this page is traceable to one of these. Where a study is small, unrandomised or industry-sponsored, that is stated in the text rather than left in the footnote.
Where this leaves you
It buys ejaculation at some cost in long-term certainty, and bleeding deserves a proper conversation rather than a reassuring number. Both are worth discussing against your own anatomy.