Introduction
Clot retention within the bladder following episodes of significant hematuria constitutes a critical urological emergency1. Conventional management strategies involve continuous bladder irrigation with 0.9% (normal saline). However, this traditional approach frequently demonstrates limited effectiveness, often necessitating prolonged and labor-intensive efforts to achieve complete clot evacuation.
Occasionally, in a tenacious and chronic blood clot, intervention with cystoscopy is required for blood clot evacuation in the operating room (OR). Evacuation with an Ellick evacuator or a Toomey syringe has a risk of bladder rupture due to the addition of positive pressure during evacuation in an overdistended bladder2,3. Surgical options are also challenging for patients in rural areas with difficult transportation access to main hospitals, in pediatric patients with small urethral calibres, and in those who are not eligible for general anesthesia or spinal anesthesia4.
Several methods have been modified to prevent open suprapubic clot evacuation and allow conducting in a bedsit with local anesthesia. One of them is intravesical agents and changes in flushing fluid elements such as anti-thrombolytic agents, hydrogen peroxide, chymotrypsin5,6. The most frequently used intravesical agent in bladder clot management was hydrogen peroxide, which was first introduced by Warlick et al. The mechanism of hydrogen peroxide remained unclear, but some theories include the inhibition of adenosine phosphate and the oxidizing effect7. Until now, there is no standard regimen, with various dosages of hydrogen peroxide varying in several studies.
Unavailable data regarding effective dosage and duration of hydrogen peroxide instillation have been a concern in use for clinical settings. Although no complications have been reported in various studies regarding this method, several studies have reported reactive oxygen species, such as induces chronic cystitis, especially in long-term duration (> 30 min) and harmful complications in animal model2,7–10.
Hydrogen peroxide offers multiple clinical benefits in bladder clot management. Its application assists in achieving hemostasis during active hemorrhage while simultaneously improving endoscopic visualization of the bladder lumen2,7. The solution effectively reduces the cohesive strength of retained clots, making them more amenable to removal2,7. This property proves particularly valuable when conventional manual irrigation becomes excessively prolonged or physically demanding for clinicians. Furthermore, as an inexpensive and readily available agent, hydrogen peroxide presents a practical solution for routine clinical use. The current investigation was designed to systematically evaluate the thrombolytic effectiveness of hydrogen peroxide by testing different concentrations and exposure times using an in vitro model simulating urinary clot retention.
Materials and methods
In vitro bladder models
This study follows the methods used by Ritch et al. For this experimental investigation, we used an in vitro bladder simulation system utilizing a 750 mL transparent urinary drainage leg bag (OneMed, Indonesia, Fig. 1)11. The model incorporated a 3-way 24 French Foley catheter (OneMed, Indonesia) connected to the drainage port to replicate clinical conditions. A fresh 100 mL of unpreserved healthy human blood was obtained using an intravenous catheter, which was then connected directly to the urine bag. The blood is stored at room temperature for 24 h to facilitate clot formation. After the clot formation is observed, we proceed to the irrigation procedure.
Figure 1. Urine leg bag with the volume of 750 cc and a 20 Fr 3-way Foley Catheter.
Procedures
Each batch of the experiment was carried out 4 times to achieve consistent results using Federer’s Formula, with a total of 30 models divided into six different groups. The experiment was done utilizing three different concentrations of hydrogen peroxide and one control using normal saline. Dilution of 3% hydrogen peroxide in normal saline is necessary to achieve 0.6%, 0.3%, and 0.15% concentration. The irrigation was done in cycles using 50 mL of irrigation fluid and indwelled for 30 s or 60 s before being pulled back using a 50 mL syringe. The maximum duration of irrigation time was 10 min for each experiment. The number of cycles given to reach a significant loss of clot volume was observed, and the percentage of clot removed was noted. The procedures were done single-blinded without the participant knowing the concentration of the solution.
Primary outcomes were the degree of difficulty, total number of instillations, and total volume of irrigant used. The secondary outcome was the percentage of clots removed. Data analysis the difficulty level of irrigation was numerically standardized and compared across models as follows11: (1) No difficulty – complete clot removal was achieved immediately without resistance; (2) minimal difficulty – all clots were removed with minimal resistance; (3) moderate difficulty – partial clot removal was possible with slight resistance; (4) significant difficulty – only some clots could be removed, encountering moderate resistance; and (5) severe difficulty – clots could not be fully removed due to an inability to evacuate them through the catheter.
Statistical analysis
The procedural outcomes were recorded in tabular format using Microsoft Excel and analyzed with the Statistical Package for Social Sciences version 26. Continuous variables were expressed as mean ± standard deviation and median (range). Statistical comparisons were conducted using non-parametric methods, specifically the Kruskal-Wallis test, followed by the Mann-Whitney U test for post hoc analysis. A p < 0.05 was considered statistically significant.
Results
In this study, different concentrations of hydrogen peroxide (H2O2) (0.15%, 0.30%, and 0.60%) were used as an irrigation agent for blood clot evacuation in bladder models. The instillation time varied between 30 s and 60 s before the evacuation procedure was attempted. The detailed results are presented in table 1.
Table 1. Differences in the degree of difficulty, total time, total cycle, and time per cycle between groups
| Intervention group | Degree of difficulty | Total time (seconds) | Total cycle (times) | Time per cycle (seconds) |
|---|---|---|---|---|
| Pure saline water 0.9% | 5.00 ± 0.00 5.00 (5.00-5.00) | 692.50 ± 20.62 690.00 (670.00-720.00) | 10.00 ± 0.00 10.00 (10.00-10.00) | 69.25 ± 2.06 69.00 (67.00-72.00) |
| H2O2 0.15% (indwelling 30 s) | 4.25 ± 0.50 4.00 (4.00-5.00) | 228.50 ± 23.69 228.00 (200.00-258.00) | 5.75 ± 0.50 6.00 (5.00-6.00) | 39.75 ± 2.36 39.00 (38.00-43.00) |
| H2O2 0.15% (indwelling 60 s | 3.50 ± 0.58 3.50 (3.00-4.00) | 303.00 ± 46.54 285.00 (270.00-372.00) | 5.25 ± 0.50 5.00 (5.00-6.00) | 57.50 ± 3.32 57.00 (54.00-62.00) |
| H2O2 0.30% (indwelling 30 s) | 2.75 ± 0.96 2.50 (2.00-4.00) | 134.5 ± 32.72 128.00 (102.00-180.00) | 3.75 ± 0.50 4.00 (3.00-4.00) | 35.75 ± 6.24 33.00 (32.00-45.00) |
| H2O2 0.30% (indwelling 60 s) | 3.50 ± 1.00 3.00 (3.00-5.00) | 177.00 ± 40.97 174.00 (130.00-230.00) | 4.50 ± 0.58 4.50 (4.00-5.00) | 39.20 ± 6.57 39.15 (32.50-46.00) |
| H2O2 0.60% (indwelling 30 s) | 3.25 ± 0.50 3.00 (3.00-4.00) | 147.25 ± 25.22 135.25 (133.50-185.00) | 3.75 ± 0.96 3.50 (3.00-5.00) | 40.14 ± 5.92 40.75 (33.38-45.67) |
| p value* | 0.018 | 0.001 | 0.003 | 0.005 |
|
* Kruskal-Wallis. |
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The use of H2O2 demonstrated superior effectiveness in removing blood clots compared to 0.9% normal saline (Fig. 2). This was evident in the significantly shorter total procedure time, fewer irrigation cycles, and reduced difficulty of clot evacuation in the H2O2 groups (Tables 2–5).
Figure 2. Complete evacuation of the blood clot.
Table 2. Comparison of the degree of difficulty between groups
| Study group | Pure saline water 0.9% | H2O2 0.15% (indwelling 30 s) | H2O2 0.15% (indwelling 60 s) | H2O2 0.30% (indwelling 30 s) | H2O2 0.30% (indwelling 60 s) | H2O2 0.60% (indwelling 30 s) |
|---|---|---|---|---|---|---|
| Pure saline water 0.9% | – | 0.040 | 0.013 | 0.013 | 0.040 | 0.011 |
| H2O2 0.15% (indwelling 30 s) | – | – | 0.096 | 0.044 | 0.169 | 0.040 |
| H2O2 0.15% (indwelling 60 s) | – | – | – | 0.222 | 0.739 | 0.495 |
| H2O2 0.30% (indwelling 30 s) | – | – | – | – | 0.278 | 0.350 |
| H2O2 0.30% (indwelling 60 s) | – | – | – | – | – | 0.850 |
| H2O2 0.60% (indwelling 30 s) | – | – | – | – | – | – |
|
Bold: significant results. |
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Table 3. Comparison of total times (seconds) between groups
| Study group | Pure saline water 0.9% | H2O2 0.15% (indwelling 30 s) | H2O2 0.15% (indwelling 60 s) | H2O2 0.30% (indwelling 30 s) | H2O2 0.30% (indwelling 60 s) | H2O2 0.60% (indwelling 30 s) |
|---|---|---|---|---|---|---|
| Pure saline water 0.9% | – | 0.019 | 0.019 | 0.019 | 0.019 | 0.019 |
| H2O2 0.15% (indwelling 30 s) | – | – | 0.019 | 0.019 | 0.144 | 0.019 |
| H2O2 0.15% (indwelling 60 s) | – | – | – | 0.019 | 0.019 | 0.019 |
| H2O2 0.30% (indwelling 30 s) | – | – | – | – | 0.144 | 0.144 |
| H2O2 0.30% (indwelling 60 s) | – | – | – | – | – | 0.559 |
| H2O2 0.60% (indwelling 30 s) | – | – | – | – | – | – |
|
Bold: significant results. |
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Table 4. Comparison of total cycles (times) between groups
| Study group | Pure saline water 0.9% | H2O2 0.15% (indwelling 30 s) | H2O2 0.15% (indwelling 60 s) | H2O2 0.30% (indwelling 30 s) | H2O2 0.30% (indwelling 60 s) | H2O2 0.60% (indwelling 30 s) |
|---|---|---|---|---|---|---|
| Pure saline water 0.9% | – | 0.011 | 0.011 | 0.011 | 0.013 | 0.013 |
| H2O2 0.15% (indwelling 30 s) | – | – | 0.186 | 0.015 | 0.032 | 0.025 |
| H2O2 0.15% (indwelling 60 s) | – | – | – | 0.015 | 0.096 | 0.044 |
| H2O2 0.30% (indwelling 30 s) | – | – | – | – | 0.096 | 0.874 |
| H2O2 0.30% (indwelling 60 s) | – | – | – | – | – | 0.222 |
| H2O2 0.60% (indwelling 30 s) | – | – | – | – | – | – |
|
Bold: significant results. |
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Table 5. Comparison of times per cycle (seconds) between groups
| Study group | Pure saline water 0.9% | H2O2 0.15% (indwelling 30 s) | H2O2 0.15% (indwelling 60 s) | H2O2 0.30% (indwelling 30 s) | H2O2 0.30% (indwelling 60 s) | H2O2 0.60% (indwelling 30 s) |
|---|---|---|---|---|---|---|
| Pure saline water 0.9% | – | 0.019 | 0.019 | 0.019 | 0.020 | 0.020 |
| H2O2 0.15% (indwelling 30 s) | – | – | 0.019 | 0.243 | 1.000 | 1.000 |
| H2O2 0.15% (indwelling 60 s) | – | – | – | 0.019 | 0.020 | 0.020 |
| H2O2 0.30% (indwelling 30 s) | – | – | – | – | 0.245 | 0.245 |
| H2O2 0.30% (indwelling 60 s) | – | – | – | – | – | 0.773 |
| H2O2 0.60% (indwelling 30 s) | – | – | – | – | – | – |
|
Bold: significant results. |
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Among the tested concentrations, H2O2 at 0.15% and 0.30% yield better results than the control, with H2O2 at 0.30% at a 30s dwell time yielding the most optimal results, with an average total time of 134.5 ± 32.72 s and 3.75 ± 0.50 irrigation cycles. In addition, this group exhibited the lowest procedural difficulty compared to the other groups.
Increasing the dwell time to 60 s at the same concentration did not result in a significant improvement in clot evacuation efficiency. Similarly, while higher H2O2 concentrations (0.60%) enhanced clot removal compared to control, they did not substantially reduce procedural difficulty compared to lower concentrations.
Overall, compared to pure saline irrigation, H2O2-assisted irrigation significantly reduced procedure time, the number of irrigation cycles, and the difficulty of blood clot evacuation, with the most effective outcome observed at a 0.30% concentration with a 30s dwell time.
Discussion
The process of hemostasis and blood clot formation in the bladder serves as a crucial physiological defense mechanism. When endothelial cells are injured, they trigger the activation of prothrombin, which is then converted into thrombin. This leads to the transformation of fibrinogen into fibrin, which binds platelets, red blood cells, and plasma together, forming blood clots. These clots develop when their formation surpasses the ability of urokinase in urine to dissolve them9. Currently, there are no established guidelines for managing bladder blood clots in either pediatric or adult patients. Several factors influence the success of manual irrigation, including the type and size of the catheter and the technique used for catheter manipulation. However, manual irrigation is often inefficient, time-consuming, and physically demanding due to the strong adhesive nature of blood clots.
Several methods have been modified to prevent open suprapubic clot evacuation and allow conducting bedside with local anesthesia, and have proved to be safe and efficient. Intravesical agents appear to be promising management in chronic bladder clots that can be conducted in bedside settings. Intravesical agents in bladder clot are also beneficial, especially in children, geriatric patients with high comorbidity, and traumatic patients who have difficulty with transurethral instrumentation and anesthesia considerations. Blood clot management agents with the lowest cost, minimal side effects, and availability of substances that could be repeated in multiple cycles with a high success rate have been considered when selecting the best intravesical agent. Despite no reported systemic adverse events, there is limited information regarding the relative safety of intravesical agents due to minimal and inadequate studies4.
The most frequently used intravesical agent in bladder clot management was hydrogen peroxide, which was first introduced by Warlick et al in the two case series in urological procedures7. Kalloo et al. previously reported that the instillation of 3% hydrogen peroxide (H2O2) significantly enhanced gastroscopic visualization in both animal and human studies. This improvement was achieved by modifying the properties of blood clots, making them less adherent, more translucent, and easier to remove11,12. The mechanism of hydrogen peroxide remained unclear, but some theories include the inhibition of adenosine phosphate and the oxidizing effect7. The efficacy of hydrogen peroxide (H2O2) in bladder clot evacuation observed in our study aligns with the mechanistic insights provided by Jessop et al., who demonstrated that H2O2 induces fibrinolysis in a concentration- and time-dependent manner13. Their in vitro experiments revealed that H2O2 increases fibrin fiber length and diameter while reducing branch point density, resulting in larger pore sizes and a more porous clot structure. These structural changes, driven by oxidative disruption of fibrin cross-linking, weaken the clot’s adhesive properties and facilitate its disintegration – a process that correlates with our findings that 0.30% H2O2 at a 30-s dwell time optimally balances efficacy and procedural efficiency. Notably, Jessop et al. reported that higher H2O2 concentrations (e.g., 3-10%) accelerated fibrinolysis but also emphasized that prolonged exposure (> 30 min) risks tissue toxicity. This mirrors our observation that increasing the concentration to 0.60% or extending dwell time to 60 s did not significantly enhance clot removal compared to 0.30% H2O2, suggesting a threshold for clinical utility. The time-dependent effect was further underscored by their finding that fibrinolysis peaked after 75-90 min in vitro, whereas our shorter indwelling times (30-60 s) achieved practical clot evacuation, likely due to the mechanical synergy of irrigation. Together, these studies highlight that low-concentration H2O2 with brief dwell times (e.g., 0.30% for 30 s) maximizes fibrinolysis while minimizing potential oxidative damage to the urothelium. Until now, there is no standard regimen with various dosages of hydrogen peroxide used in several studies. Low concentrations of 0.3% and 0.15% hydrogen peroxide mixed with saline solution have been described in a limited number of studies with various indwelling times and total cycle2,7–9,14.
There are several case reports and case series regarding this topic; however, a bigger population-based study is still limited, as there was only one study in 2020 by Xu et al. involving 31 patients8. A bladder irrigation solution was prepared by diluting 3% hydrogen peroxide in a 1:5 ratio with 0.9% normal saline. This solution was introduced into the bladder through a 20-Fr three-way Foley catheter in volumes of 30-50 mL, retained for 3-5 min, and then evacuated. The study demonstrated that using 0.6% hydrogen peroxide over four irrigation cycles significantly improved blood clot removal. Large clots are fragmented into smaller pieces, increasing the efficiency of manual bladder washout over time.
In 2023, Stride et al. reported a case in which a similar 3% hydrogen peroxide solution, diluted in a 1:5 ratio with normal saline, was used9. The mixture was instilled via a 20-Fr three-way Foley catheter, retained for 3 min, and then aspirated, with the process repeated for four cycles. After the fourth cycle, the patient experienced abdominal discomfort. An abdominal ultrasound showed a reduction in clot size, and no procedure-related complications were reported9.
Increasing the concentration of hydrogen peroxide led to a proportional reduction in the number of irrigation cycles required. However, no significant differences were noted in the difficulty of irrigation or the volume of irrigant used. This suggests that in cases of clot retention, combining intravesical hydrogen peroxide instillation with irrigation may be more effective than using sterile water alone. In addition, hydrogen peroxide-assisted manual irrigation could help minimize the need for operative intervention in the cystoscopic suite, potentially reducing associated morbidity.
The use of hydrogen peroxide provides several benefits, including enhancing hemostasis in cases of active bleeding, improving bladder visualization, reducing the adhesive nature of bladder blood clots, and facilitating clot disruption when manual irrigation is inefficient and labor-intensive. In addition, hydrogen peroxide is inexpensive and readily available for daily use2,8,13,15,16. Minimizing the need for cystoscopic clot evacuation could potentially avoid a costly and risky emergent trip to the OR if hydrogen peroxide is used to facilitate irrigation. Under Indonesia’s current National Health coverage, the cost of OR time for cystoscopy and clot evacuation ranges from approximately $500 to $700. In contrast, the cost of 50 mL of hydrogen peroxide is < $1, highlighting a significant cost difference between surgical intervention and hydrogen peroxide-assisted irrigation.
Despite all of the advantages, hydrogen peroxide can cause vasoconstriction, thrombus formation from platelet aggregation, free diffusion through vessel walls, and its conversion to water and oxygen to the creation of intraluminal bubbles, which leads to microembolism, thermal injury, and arteriolar spasm. Despite this theoretical consideration, no complication has been reported2,7. Dogishi et al. also reported that a chronic cystitis model can be made using 1.5% H2O2 solution instilled and indwelled in the rat bladder for 30 min10. Histopathological analysis revealed severe tissue damage, including hemorrhage, edema, urothelial denudation, intermittent rupture of the smooth muscle layer, and early infiltration of inflammatory cells such as neutrophils and mast cells. These changes led to rapid but short-term hyperpermeability of the urothelial barrier in the mouse model. Although the initial damage gradually healed, it persisted for an extended period10. However, Wu et al. reported no clinically significant histological changes in the antrum and duodenal bulb following hydrogen peroxide therapy, supporting its safety12.
Uroepithelial stem cells play a crucial role in repair processes. Unlike the epithelia found in the skin or the lining of the gut, which regenerate every 1.5-30 days, the uroepithelium has a slower turnover rate, estimated at approximately 3-6 months. Nevertheless, the uroepithelium exhibits remarkable regenerative abilities, often restoring its integrity within days following significant damage. In contrast to other tissues, uroepithelial stem cells are believed to originate from a single clone, have a slow replication cycle, yet possess a high capacity for regeneration, giving rise to various differentiated cell types17.
Other intravesical agents, like anti-thrombolytic agents, such as streptokinase and alteplase, have also been used with promising results6. These studies concluded that there was a high margin of safety with no evidence of systemic fibrinolytic complications even at higher doses. Chymotrypsin combination with 5% sodium bicarbonate is also used as an intravesical agent18. However, the cost-benefit of these products was low, and the availability in overall hospitals is questioned.
Like any in vitro study, this research has several limitations. The use of a plastic bladder model does not fully replicate the effectiveness of manual clot evacuation in a compliant structure like the human bladder. In addition, the biomechanical properties, such as elasticity and viscoelasticity, were not accounted for in the models. Enhancements, particularly in hydrodynamic design, are necessary to better simulate turbulent stress. Furthermore, the bladder’s capacity should be adjusted according to the physiological limits of the human bladder or scaled proportionally to align with the mechanical-biological characteristics of the dynamic urinary environment.
Despite these limitations, the findings from this study strongly support further investigation into the use of hydrogen peroxide for manual bladder irrigation. While clinical applications have been explored in several studies, the conflicting histopathological findings reported by Dogishi et al. should be validated in an animal model to confirm the safety of low-concentration hydrogen peroxide instillation in the bladder10. Nevertheless, these preliminary results suggest that this technique may enhance the effectiveness of bladder irrigation, particularly in cases of persistent clot formation.
Conclusion
This study identifies 0.30% hydrogen peroxide instillation with a 30-s dwell time as the most effective approach for clot evacuation. However, further in vivo animal studies and long-term assessments are needed to evaluate its safety, efficacy, and clinical applicability.
Funding
The authors declare that this work was carried out with the authors’ own resources.
Conflicts of interest
The authors declare that they have no conflicts of interest.
Ethical considerations
Protection of human subjects and animals. The authors declare that the procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation and with the World Medical Association and the Declaration of Helsinki. The procedures were authorized by the Institutional Ethics Committee.
Confidentiality, informed consent, and ethical approval. The authors have followed their institution’s confidentiality protocols, obtained informed consent from all patients, and secured approval from the Ethics Committee. SAGER guidelines have been followed as applicable to the nature of the study.
Declaration on the use of artificial intelligence (AI). The authors declare that no generative artificial intelligence was used in the writing or creation of the content of this manuscript.
