What Is a Bladder Washout and Why Is It Done?

A bladder washout is a procedure in which fluid, usually sterile saline, is flushed into the bladder through a catheter and then drained back out. It is done to clear debris, blood clots, or mineral deposits that can block a catheter, and sometimes to deliver medication directly to the bladder lining. The procedure sounds simple enough, but the reasons for doing it, the solutions used, and the evidence behind it are more varied than most people expect.

How the Procedure Actually Works

In its most basic form, a bladder washout involves connecting a syringe or bag of fluid to an existing urinary catheter, pushing fluid into the bladder, and then letting it drain out by gravity or gentle suction. The idea is that the flowing liquid loosens whatever is causing trouble inside the bladder or catheter, whether that is a blood clot, a crust of calcium crystite, or a colony of bacteria clinging to the catheter surface.

There are two broad approaches. Manual irrigation uses a large syringe (often 50 or 60 mL) to push fluid in, pause briefly, and then withdraw it. Continuous bladder irrigation, or CBI, uses a three-way catheter with a dedicated inflow port so fluid can run in continuously from a hanging bag while draining out through a separate channel. Research on three-way catheters shows that brand and size matter: in bench testing, some 22-French and 24-French catheters delivered significantly better flow through the irrigation port than others, with continuous irrigation flow rates ranging from about 1.6 to 1.7 mL per second in the higher-performing models.

Automated systems are also in development. A preclinical study using a porcine model found that an automated intermittent irrigation system removed test material more effectively than manual irrigation performed by an experienced urologist, with removal rates around 94% versus 89%. The automated approach was faster and more consistent, and it kept pressures within safe physiological limits throughout.

Clearing Blood Clots After Surgery

One of the most common reasons for bladder irrigation, particularly in hospitals, is to prevent or clear blood clots after urological surgery. Procedures on the prostate, bladder, or kidneys often leave raw surfaces that ooze blood into the urine. If that blood pools in the bladder and clots, it can block the catheter entirely, a situation called clot retention. The bladder distends painfully, urine cannot drain, and if nothing is done, the backed-up pressure can damage the kidneys.

Postoperative bleeding can result from incomplete control of bleeding vessels during surgery, or from straining or increased activity afterward.³ Continuous bladder irrigation with saline is the standard preventive measure: the steady flow of fluid dilutes the blood and flushes small clots out before they grow large enough to block the catheter. When a patient already has clot retention, manual washout with a large syringe is used to break up and extract the clots. A protocol study on clot retention recommended using at least a 22-French catheter, practicing strict infection control, and following what the authors called a “last clot plus one litre” rule, meaning you continue irrigating for an additional litre of clear fluid after the last visible clot is removed.⁴

Temperature of the irrigation fluid also matters in the surgical setting. A meta-analysis of studies on prostate surgery patients found that using warmed irrigation fluid (rather than room-temperature fluid) significantly reduced the risk of shivering and hypothermia during the procedure. The risk of shivering dropped by roughly two-thirds with warm fluid, and body temperature remained more stable throughout surgery.⁵

Preventing Catheter Blockages in Long-Term Catheter Users

The other major use of bladder washouts is for people living with long-term indwelling catheters, meaning catheters that stay in place for weeks to months. Over time, minerals from urine, particularly calcium and magnesium phosphate, can crystallize on the catheter surface. This encrustation gradually narrows the drainage channel until the catheter blocks completely. Some people are “blockers” whose urine chemistry makes this happen frequently, while others go months without trouble.

The theory behind scheduled washouts is straightforward: flushing the catheter and bladder regularly should dissolve or dislodge encrustation before it becomes a full blockage. Acidic washout solutions like Suby G (a citric acid-based solution) are specifically designed for this purpose. Lab research has shown that Suby G can dissolve encrusting material when retained in the catheter for about 15 minutes, with the dissolved calcium and magnesium measurable in the returned fluid.⁶

Whether this laboratory effect translates into a clinical benefit for patients has been harder to pin down. A Cochrane systematic review concluded that the evidence was not adequate to determine whether washouts were beneficial or harmful for long-term catheter users, and called for higher-quality trials.⁷

What the CATHETER II Trial Found

The evidence picture improved somewhat with the publication of the CATHETER II randomized controlled trial, the largest study to date comparing washout policies in people with long-term catheters. The trial assigned participants to one of three groups: saline washouts, acidic washouts, or no washouts at all. Both washout groups showed about half the rate of catheter blockages requiring treatment compared with the no-washout group, with roughly 10 blockages per 1,000 catheter days in the washout groups versus about 21 per 1,000 catheter days in the control group. However, this difference did not reach statistical significance, meaning the result could plausibly be due to chance given the sample size.⁸

The more striking finding involved urinary tract infections. Participants who received saline washouts had a significantly lower rate of symptomatic catheter-associated UTIs requiring antibiotics, at roughly 3.7 episodes per 1,000 catheter days compared with about 8 episodes per 1,000 catheter days in the control group. The acidic washout group fell in between, at about 6.7 per 1,000 catheter days, and did not differ significantly from the no-washout group. The authors cautioned that the small sample size means these findings should be interpreted carefully.⁹

A subsequent systematic review with meta-analysis that incorporated the CATHETER II data also noted that washout groups tended to have slightly better quality-of-life scores than no-washout groups, though the differences were not statistically significant.¹⁰

So the honest state of the evidence is suggestive but not yet definitive. Washouts, particularly with saline, appear to help, but clinicians and patients are still making decisions based on incomplete data. For someone whose catheter blocks regularly, the potential benefit is clear enough to justify trying. For someone whose catheter rarely blocks, the case is weaker.

Saline Versus Acidic Solutions

Most routine bladder washouts use normal saline, which is inexpensive, widely available, and well tolerated. It works primarily by mechanical flushing, physically dislodging debris and diluting anything that might form a plug. Saline does not dissolve mineral deposits, but it does not need to if the encrustation has not yet hardened.

Acidic solutions like Suby G (citric acid) or Solution R (a stronger citric acid formulation) are designed to chemically dissolve calcium and magnesium deposits. In theory, this should make them more effective for people with heavy encrustation. Yet the CATHETER II trial found that acidic washouts performed similarly to saline washouts for preventing blockages, and saline actually came out ahead for reducing UTIs.¹¹ One possible explanation is that the acidic solutions irritate the bladder lining, which could promote inflammation and make infections more likely, but this has not been conclusively demonstrated.

The choice of irrigating fluid becomes more consequential in surgical settings, where large volumes are absorbed. A case study of a dialysis patient who received prolonged bladder irrigation documented a weight gain of 7.4 kg in 24 hours from massive fluid absorption, ultimately leading to fatal pulmonary edema.¹² Even normal saline, generally considered safe, can cause metabolic problems in large volumes: one case report described a patient who developed metabolic acidosis and hemodilution after absorbing a large volume of saline during prostate surgery.¹³ These are extreme scenarios, mostly relevant to operating rooms where the bladder wall has been disrupted, but they underscore why irrigation is not a procedure to treat casually.

Antimicrobial Instillations for Recurrent Infections

A related but distinct use of the same basic technique is instilling antibiotics or antiseptics directly into the bladder to treat or prevent recurrent urinary tract infections. This is sometimes called intravesical therapy, and while it shares the mechanics of a bladder washout (fluid goes in through a catheter, sits in the bladder, then comes out), its purpose is pharmacological rather than mechanical.

The rationale is that delivering antibiotics straight to the infection site allows much higher local drug concentrations than oral or intravenous antibiotics can achieve, because some drugs penetrate poorly into the bladder from the bloodstream. Agents like gentamicin, amikacin, and colistin can disrupt bacterial biofilms, the protective structures bacteria build on catheter surfaces that make them resistant to standard treatment.¹⁴ Because the antibiotic stays in the bladder rather than circulating through the whole body, it may also reduce selective pressure on bacteria elsewhere, potentially slowing the development of resistance.¹⁵

A systematic review of antimicrobial intravesical treatment found that roughly four out of five patients experienced a meaningful reduction in symptomatic UTIs, with short-term success rates of about 71% in prophylaxis groups and 88% in treatment groups. Discontinuation rates were low, suggesting most patients tolerated the instillations well.¹⁶ That said, the studies that make up this evidence base tend to be small, and changes in the sensitivity of organisms were observed in roughly a quarter to a third of cases, meaning resistance can still develop even with local delivery.

Intravesical therapy extends beyond infections. For people with non-muscle-invasive bladder cancer, oncologists instill chemotherapy agents or immunotherapy (such as BCG or mitomycin C) directly into the bladder after tumor removal to reduce the chance of recurrence.¹⁷ This uses the same catheter-based delivery mechanism but is a fundamentally different clinical situation from a maintenance washout for catheter blockages.

When Washouts Do Not Help

Not every bladder problem responds to irrigation. One area where the evidence is discouraging is using washouts to clear bacteria from the urine. A randomized study of 89 people with neurogenic bladders and bacteriuria had participants irrigate their bladders twice daily for eight weeks with either saline, acetic acid, or a neomycin-polymyxin antibiotic solution. None of the three had any detectable effect on the degree of bacteria or inflammation in the urine. The authors concluded that bladder irrigation could not be recommended as a treatment for bacteriuria in this population.¹⁸

This matters because many people with catheters have bacteria in their urine without symptoms, a condition called asymptomatic bacteriuria. The temptation to “wash it out” is understandable but unsupported. Current practice generally distinguishes between asymptomatic bacteriuria, which does not require treatment, and symptomatic infection with fever, pain, or cloudy foul-smelling urine, which does. Washouts occupy a role in prevention and catheter maintenance rather than in treating established bacterial colonization.

Doing Washouts at Home

For people with long-term catheters living at home, washouts do not have to be a hospital procedure. The CATHETER II trial specifically trained participants to self-administer their washouts, with or without help from a carer.⁹ The mechanics are straightforward: pre-filled sachets of saline or acidic solution attach to the catheter, the fluid runs in by gravity, is held for a few minutes, and then drains into a bag. Community nurses typically teach the technique during an initial visit.

A separate randomized trial evaluated a broader self-management program for long-term catheter users that included washout training alongside other skills. That study did not find significant differences in catheter-related quality of life between the intervention and control groups.¹⁹ This may reflect the reality that catheter life involves many sources of discomfort and disruption, and addressing one of them does not necessarily move the overall quality-of-life needle. It does not mean the washouts were useless for catheter maintenance; it means the benefits may be more functional (fewer emergency visits for blocked catheters) than subjective.

If you are considering washouts at home, the practical considerations include keeping everything sterile during the connection and disconnection steps, recognizing signs of a blockage that needs professional attention (complete inability to drain, severe pain, fever), and tracking how often blockages occur so your care team can adjust the washout frequency. Most protocols call for washouts once or twice a week, though people who block frequently may need them more often.

Washouts for Children with Neurogenic Bladders

Children born with conditions like spina bifida often have neurogenic bladders that do not empty properly and require intermittent catheterization from an early age. These children are at high risk of recurrent UTIs and, over years, of kidney damage. The challenge is that their altered urinary tracts tend to become colonized with bacteria, and it can be genuinely difficult to tell whether a positive urine culture represents a dangerous infection or harmless colonization. Some children end up overtreated with antibiotics for what is actually benign bacteriuria, while others may be undertreated for genuinely threatening infections.²⁰

In this population, bladder washouts with non-antibiotic solutions, including newer electrochemically activated formulations, are being explored as a preventive strategy. The appeal is clear: if regular washouts can reduce bacterial load without using antibiotics, they might break the cycle of recurrent infections, repeated antibiotic courses, and inevitable resistance. Research in this area is still early, but the concept reflects a broader movement in urology toward catheter maintenance strategies that reduce antibiotic dependence rather than adding to it. For families managing a child’s neurogenic bladder, washouts represent one more tool in what is usually a complex and long-term care routine.