Causes of damage of single use ureteroscope: a single center 2-year experience

doi:10.21203/rs.3.rs-5850232/v1

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Causes of damage of single use ureteroscope: a single center 2-year experience

https://doi.org/10.21203/rs.3.rs-5850232/v1

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published 14 Oct, 2025

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Background

Since the evolution of flexible ureteroscopy from being reusable to disposable then reused disposable scopes aimed basically to reduce the cost, this study was conducted to evaluate the causes of reused disposable flexible ureteroscope damage in order to extend its longevity and increase the number of procedures per scope.

Patients and Methods:

This retrospective study was conducted in a single center between September 2022 and September 2024. Sixty-two reused disposable flexible ureteroscopes after resterilization were used for 202 patients over 235.7 hours. Potential causes of scope damage were observed, recorded and analyzed.

Results

The observed causes of reused disposable flexible ureteroscope damage were as follows: 32.3% of scopes were damaged by laser fiber related damage (either by sudden withdrawal of fiber during firing or transmitted energy), 27.4% by sustained excessive deflection, 19.4% by scope backloading technique, 9.6% by traumatic ureteral access sheath usage (such as scope withdrawal while deflected over the access sheath and stone fragment lodgment between the sheath and scope) and 11.3% by instrumental working channel damage. On comparing different related causes of damage, fine deflection proved to be superior to excessive deflection (p < 0.001) and access sheath usage proved to be significantly superior to backloading (p = 0.005) while there were no significant difference on comparing laser settings.

Conclusion

Longevity of su-FURS can be extended through the avoidance of possible causes of damage. The best cost effective practice can be achieved by performing flexible ureteroscopy with avoidance of scope backloading in tight ureter and using of ureteral access sheath, avoidance of excessive deflection by lower calyceal stone relocation and avoidance of in-situ disintegration and insertion of laser fiber in a straight scope before deflection with careful holding of the fiber to avoid its sudden withdrawal while firing inside the scope.

reused disposable flexible ureteroscope

flexible ureteroscopy

scope damage

durability

longevity

Since the first use of flexible ureteroscope (FURS), FURS has been advancing (1, 2). Therefore, the use of FURS has increased rapidly and widely utilized for both diagnostic and therapeutic purposes for many upper urinary tract pathologies (3). Less invasive procedures, shorter operative time, higher stone free rate, and shorter length of hospital stay resulted from this technology advancement (4).

The reusable flexible ureteroscope (re-FURS) has proved to have enhanced manoeuvrability because of its small scope diameter. However, the costs of purchasing, maintenance and repair are high (5, 6). The Scopes will require frequent repair after only 12–15 procedures (7). Additionally, many studies suggest that scope failure will occur at an average of 9–50 cases (8, 9).

The development of single use flexible ureteroscope (su-FURS) has eliminated the need for scope maintenance and repair along with their high costs (5, 10). Furthermore, in countries with limited resources, su-FURS is believed to be resterilized and reused as a cost-conscious approach with a low infectious complication rate (11). Nevertheless, su-FURS can be damaged by several causes such as excessive stress on the deflection mechanism, fault insertion of the laser fiber or basket and the traumatic usage of ureteric access sheath (UAS) (12).

The aim of this study is to evaluate and analyse the causes of reused disposable flexible ureteroscope (rd-FURS) damage.

This retrospective study was conducted in a single center between September 2022 and September 2024. The study included 62 reused disposable flexible ureteroscopes which were used for 202 procedures over a duration of 235.7 hours. The study received ethics approval from our local university ethics committee under the number 12-2024UROL13.

We performed all procedures using su-FURS. The used su-FURS included a 7.4Fr tip diameter and 8.6Fr outer diameter with full 275-degree scope active deflection in both directions (WiScope® Single-Use Digital Flexible Ureteroscope), a 7.7Fr tip diameter and 9.5Fr outer diameter with full 270-degree scope active deflection in both directions (LithoVue™ Single-Use Digital Flexible Ureteroscope, Boston scientific), a 8.4Fr uniform outer diameter with full 285-degree scope active deflection in both directions (Scivita Medical single-use Videoscope). In pre-stented or non-tight ureters, a 10/12Fr Elephant II Flexible & Navigable Suction Access Sheath (FANS), (YiGaoMed, China) were used. Endoscopic lithotripsy was conducted by Holmium:YAG laser lithotripsy (Sphinx 30 Litho ®, katlenburg-Lindeau, Germany) and using Laser fiber (SureFib reusable 272 µm laser fiber). Renal stones were extracted using nitinol baskets (The Dakota™ nitinol basket 1.9F, Boston Scientific, Natick, MA, USA).

All scopes were sterilized prior to reusing using low-temperature hydrogen peroxide gas. The process occurred at a temperature 18–35°C with average total time of 40 minutes. sterilization procedures were conducted by specialized sterilization personnel.

Patients who had renal stone(s) diagnosed by abdominopelvic CT with negative preoperative urine culture were included while patients who were unfit for surgery or with active urinary tract infection were excluded.

Based on the European Association of Urology guidelines 2024 recommendations, all patients received a single dose of prophylactic antibiotic (Fluoroquinolones) preoperatively. Under general anaesthesia, procedures were undergone by experienced staff in supine lithotomy position. Flexible ureteroscopies were preceded by 2–4-week double J stenting in the majority of cases. Following flexible ureteroscopies, all cases had a double J stent inserted for 2–4 weeks then removed.

Data on the total duration and number of usage times for each scope were recorded. Possible causes of FURS damage were observed and recorded.

Statistical analysis of the data

Data were fed to the computer and analysed using IBM SPSS software package version 20.0. (Armonk, NY: IBM Corp, released in 2011). Categorical data were represented as numbers and percentages. Chi-square test was applied to compare between two groups. Alternatively, Fisher Exact correction test was applied when more than 20% of the cells have expected count less than 5. For continuous data, they were tested for normality by the Kolmogorov-Smirnov test. Quantitative data were expressed as range (minimum and maximum), mean, standard deviation and median Student t-test was used to compare two groups for normally distributed quantitative variables while. On the other hand, Mann Whitney test was used to compare two groups for not normally distributed quantitative variables while Kruskal Wallis test was used to compare different groups for not normally distributed quantitative variables. Significance of the obtained results was judged at the 5% level.

Regarding stone characters, 25 stones were in lower calyx (40.3%), 18 (29.0%) of which were disintegrated in place while 7 (11.3%) were disintegrated after relocation to another site in the pelvicalyceal system, 14 stones were in middle calyx (22.6%), 11 stones were in renal pelvis (17.7%), 8 stones were in pelvi-ureteric junction (12.9%) and 4 stones were in upper calyx (6.5%). The median stone volume was 1775 mm³ and the median Hounsfield unit was 900 HU. The majority of stones were radio-opaque (88.7%) while only 4.8% and 6.5% were radio-faint and lucent respectively. 64.5% of procedures were preoperatively stented with double J (Table 1).

Regarding postoperative complications, fever was reported after 40 procedures out of 202 procedures (19.8%) and hematuria was reported after 13 procedures out of 202 procedures (6.4%). The postoperative fever was not associated with serious sepsis in any of our cases. Moreover, fever following the first su-FURS use was observed in 9 out of 62 cases (14.5%) versus 31 out 140 cases (22.1%) following resterilized rd-FURS with no significant difference between both (p = 0.209) (Table 1).

Data on the longevity and device burden per scope was demonstrated in (Table 1). Median scope lifespan was 3 hours and median number of procedures undergone by each scope was 3 procedures with a median procedure duration of 1.17 hours. Dormia was used in 40.3% of procedures.

Table 1

treatment characteristics, device longevity and burden
Treatment characteristics
Stone site, n (%)
Upper calyx	4 (6.5%)
Middle calyx	14 (22.6%)
Lower calyx	25 (40.3%)
Lower calyx stone (disintegrated in-situ)	18 (29.0%)
Lower calyx stone (disintegrated after relocation)	7 (11.3%)
Pelvi-ureteric junction	8 (12.9%)
Renal pelvis	11 (17.7%)
Median stone Volume, mm³ (IQR)	1775.0 (1500.0–3000.0)
Stone radio-opacity, n (%)
Opaque	55 (88.7%)
Faint	3 (4.8%)
Lucent	4 (6.5%)
Median Hounsfield unit, HU (IQR)	900.0 (800.0–1000.0)
Procedures with preoperative double J stenting, n (%)	40 (64.5%)
Postoperative reported complications, n (%)	53/202 (26.2%)
Hematuria	13/202 (6.4%)
Fever	40/202 (19.8%)
Fever following the first su-FURS use	9/62 (14.5%)	P value = 0.209
Fever following the resterilized rd-FURS use	31/140 (22.1%)	P value = 0.209
Longevity and device burden per scope
Median scope lifespan, h (IQR)	3.00 (2.00–5.25)
Median number of procedures, n (IQR)	3 (2–5)
Median procedure duration, h (IQR)	1.17 (1.00–1.33)
Procedures with access sheath usage, n (%)	43 (69.4%)
Procedures with dormia basket usage, n (%)	25 (40.3%)

HU, Hounsfield unit; IQR, interquartile range; SD, standard deviation; su-FURS, single use flexible ureteroscope; rd-FURS, reused disposable flexible ureteroscope.

Causes of scope damage were analysed. The most prevalent cause for scope damage was laser fiber related damage in 20 scopes (32.3%) followed by sustained excessive deflection in 17 scopes (27.4%). Scope backloading technique caused damage to 12 scopes (19.4%) while traumatic UAS usage was associated with damage of 6 scopes (9.6%). Instrumental working channel damage caused damage to 7 (11.3%) scopes (Table 2).

Table 2

Causes of damaged scopes.
Cause of damage	Number (%)
Scope backloading, n (%)	12 (19.4%)
Laser fiber related damage, n (%)	20 (32.3%)
Sustained excessive deflection, n (%)	17 (27.4%)
Traumatic access sheath usage, n (%)	6 (9.6%)
Instrumental working channel damage, n (%)	7 (11.3%)

Different related causes of damage were compared to each other. Comparison between laser settings, high and low energy settings, showed no significant difference between both arms of comparison either for the overall number of damaged scopes (p = 0.098) or the specific causes of damage either sudden withdrawal of laser fiber during firing or transmitted energy (p = 0.568) (Table 3).

Regarding scopes damaged by loss of deflection system, there were 15 damaged scopes out of 18 scopes that experienced excessive deflection (83.3%) versus 2 damaged scopes out of 44 scopes that experienced fine deflection (4.5%) which represented a statistically significant difference (p < 0.001) (Table 3).

Another comparison between scope backloading and UAS usage showed a significant difference between both groups regarding the overall number of damaged scopes (p = 0.005) while there was no difference regarding the specific causes of damage including guide wire malfunction, stone fragment lodgement, ureteric resistance and scope withdrawal while deflected over the UAS (p = 0.332) (Table 3).

Table 3

Comparisons between different related causes of scope damage.
	High energy laser setting (2J/10Hz) (n = 34)	Low energy laser setting (1J/15Hz) (n = 28)	P-value
Damaged scopes, n (%)	14/34 (41.2%)	6/28 (21.4%)	0.098
Cause of damage
Sudden fiber withdrawal, n (%)	10 (71.4%)	5 (83.3%)	0.573
Transmitted energy, n (%)	4 (28.6%)	1 (16.7%)	0.573
	Excessive deflection (n = 18)	Fine deflection (n = 44)	P-value
Damaged scopes by loss of deflection system, n (%)	15/18 (83.3%)	2/44 (4.5%)	< 0.001
	Scope backloading (n = 19)	Access sheath usage (n = 43)	P-value
Damaged scopes, n (%)	12/19(63.1%)	6/43(13.9%)	0.005
Cause of damage
Guide wire malfunction, n (%)	5 (41.7%)	1 (16.6%)	0.332
Stone fragment lodgment, n (%)	5 (41.7%)	4 (66.8%)
Ureteric resistance, n (%)	2 (16.6%)	0 (0.0%)
scope withdrawal while deflected over the access sheath, n (%)	0 (0.0%)	1 (16.6%)

Over the last decade, su-FURS has proven to be a comparable alternative to re-FURS (13). There is a lack of clinical evidence supporting su-FURS standard use or its specific indications despite the fact that su-FURS have advantages over reusable ones (14). The evolution of reusing su-FURS approach aimed to decrease the cost of su-FURS usage without affecting postoperative outcomes (11). In order to prolong the durability of disposable scopes and increase the number of procedures per scope, our study aimed to highlight the common causes of rd-FURS damage.

To the best of our knowledge, no previous studies investigated the causes of rd-FURS. However, Sugino et al, (2022) evaluated factors associated with microdamage to su-FURS following a single procedure (15). Multiple studies discussed causes that contributed to re-FURS damage either through data collected from the manufacturer or by direct scope evaluation (1, 16, 17).

This study included 62 rd-FURS used for 202 procedures, with median procedures per scope of 3 procedures, over duration of 235.7 hours with median scope lifespan of 3 hours. The most frequent cause of damage was mediated by laser fiber which we observed in 32.3% of the damaged scopes. Since stone ureteroscopy was the only indication for flexible ureteroscopy in our procedures, laser was used in all procedures either in high energy laser setting (2J/10Hz) or low energy laser setting (1J/15Hz). Consequently, we compared the overall number of damaged scopes in both setting groups to each other with no significant difference between both groups. Additionally, we compared the specific mode of damage in both setting groups including transmitted energy and sudden laser fiber withdrawal during firing with no significant difference between both groups.

On the contrary, Sugino et al, (2022) founded that laser energy was not associated with the risk of scope damage (15). This may be attributed to the fact that laser energy effect is believed to be accumulated over multiple procedures. As a confirmation to this, Juliebø-Jones et al, (2023) showed that direct laser energy caused damage to 23 (15.6%) of the damaged re-FURS versus 0% of the damaged su-FURS (17). Moreover, Sung et al,(2005) showed that laser energy damage was the primary cause of re-FURS damage by causing burns and punctures to working channel, optic fibers, shaft and even to the deflection components (6).

Loss of deflection system was the second most frequent mode of damage that was observed in 27.4% of the damaged scopes. Loss of deflection system is believed to result from excessive, sustained and prolonged deflection which occur mostly in lower calyceal stones management. We compared the deflection for lower calyx stone disintegration in-situ versus the deflection for relocated lower calyx stones to another site in pelvicalyceal system, upper and middle calyceal, pelvic and pelvicalyceal stones. Lower calyceal stone disintegration in-situ required excessive deflection while the other stones required only fine or no deflection. This comparison revealed that stones that required excessive deflection caused deflection system failure more than stones that required fine or no deflection with a statistically significant difference.

Deflection failure was observed in 5 out of 30 su-FURS in the study by Sugino et al, (2022) representing the most common cause of microdamage to su-FURS (15). Juliebø-Jones et al, (2023) likewise found that deflection failure occurred in 8 (5.4%) of the damaged re-FURS and 2 (3.4%) of the damaged su-FURS (17). Loss of deflection was considered the most frequent cause of re-FURS damage in the review article by Hosny et al, (2019)(1). Ozimek et al, (2018), who focused on the steep infundibulo-pelvic angle as a risk factor for re-FURS damage, showed that lower calyceal stones with steep infundibulo-pelvic angle were present in 60.53% of the damaged FURS regardless of the complexity of the stone (18). Additionally, Sung et al, (2005) showed that 15% of the damaged re-FURS were attributed to the failure of deflection system (6).

One of the most frequently observed causes of damage was the scope backloading in 17.7% of the damaged scopes. Although the use of UAS was one of the damage causes, we found that UAS usage was superior to scope backloading without UAS usage. On comparing UAS usage to backloading, 6 scopes were damaged out of 43 scopes in which UAS used (13.9%) versus 12 damaged scopes out of 19 scopes used by backloading technique (63.1%) which represents a statistically significant difference. Nevertheless, when we compared both groups regarding the specific causes of damage (such as stone fragment lodgment, ureteric resistance and guidewire malfunctions), there was no significant difference.

In alignment to our findings, Multescu et al, (2014) considered that prolonged lifespan of re-FURS was significantly associated with UAS usage by reducing the resistance during insertion in addition to its beneficial ease of stone fragments removal and minimizing the intrarenal pressure (19). However, many studies have stated theories about damage mediated by UAS usage including bending of deflected FURS against the tip of the UAS, stone fragment lodgement between the FURS and UAS during forcible removal of the scope (1).

Instrument mediated working channel damage was observed in minority of the damaged scopes in this study in 11.3% of the affected scopes. Sugino et al, (2022) showed that instrumental working channel damage such as using basket wire catheter represents a risk factor for su-FURS damage (15). Similarly, Juliebø-Jones et al, (2023) found that damaged working channel by basket occurred in 9 (6.1%) of the damaged re-FURS while 0 (0%) of the damaged su-FURS (17). On the other hand, the working channel accounted for the highest percentage of repairs in 52% of the damaged re-FURS as reported by Sung et al, (2005) (6).

Gauhar et al, (2024) observed Postoperative fever in 13.7% of the cases in which rd-FURS was used while we observed fever in 22.1% of the cases in which resterilized rd-FURS was used (11). We likewise compared postoperative fever following the first su-FURS use to that following resterilized rd-FURS. However, this difference did not reach the significance level.

Our study allowed the evaluation of rd-FURS regarding causes of damage which to our knowledge is a novel study. We managed to observe these causes when using different types of su-FURS which may enhance the robustness of our results. However, there were a few limitations that needed to be addressed. One of these limitations was the relatively small number of evaluated scopes. Additionally, procedures were undergone under different surgical situations and surgeons.

We believe our study would contribute to prolongation of su-FURS longevity, avoidance of its damage causes and consequently, reduction of flexible ureteroscopy procedure costs.

Longevity of su-FURS can be extended through the avoidance of possible causes of damage. The best cost effective practice can be achieved by performing flexible ureteroscopy with avoidance of scope backloading in tight ureter and using UAS, avoidance of excessive deflection by lower calyceal stone relocation and avoidance of in-situ disintegration and insertion of laser fiber in a straight scope before deflection with careful holding of the fiber to avoid its withdrawal and firing inside the scope.

Flexible ureteroscope

FURS

single use flexible ureteroscope

su-FURS

reusable flexible ureteroscope

re-FURS

reused disposable flexible ureteroscope

rd-FURS

ureteric access sheath

UAS

Flexible & Navigable Suction Access Sheath

FANS.

Ethics approval and consent to participate statement:

The study received ethics approval from our local university ethics committee (institutional review board [IRB]) under the number 12-2024UROL13. We obtained informed consent from all patients prior to participating in the study.

Consent for publication statement:

Not applicable.

Funding statement:

No funding was received for conducting this study or to assist with the preparation of this manuscript.

Author Contribution

M.E. conceived the idea and design of the work. A.A. wrote the main manuscript text. H.K. collected the data. M.A. did the data analysis and interpretation. All authors reviewed the manuscript.

Acknowledgement

The authors would like to express gratitude towards all the patients who participated in our study.

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No competing interests reported.

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You are reading this latest preprint version

Causes of damage of single use ureteroscope: a single center 2-year experience

Status:

Journal Publication

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Abstract

Background

Patients and Methods:

Results

Conclusion

Introduction

Patients and methods

Statistical analysis of the data

Results

Discussion

Conclusion

Abbreviations

Declarations

Author Contribution

Acknowledgement

References

Additional Declarations

Status:

Journal Publication

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