Improving Flexible Ureterorenoscope Durability Up to 100 Procedures

Abstract

Background and Purpose:

Controversy exists in the literature regarding flexible ureterorenoscopy (F-URS) durability, with a variable expected number of uses from a new F-URS. In this study, a tertiary center experience with the use of two consecutive F-URS is reported and suggestions as to how to improve durability further are made.

Materials and Methods:

All F-URS performed in the same tertiary care center between July 2009 and February 2011, with two new instruments Flex-X, were reviewed retrospectively. All renal pathology were included. Ureteral cases were excluded. A 9.5F semirigid ureteroscope was always used at the start for a ureteral optical predilation and to explore the upper urinary tract for possible lithotripsy/laser ablation/biopsy. The F-URS was introduced sequentially to explore the remaining calices. Data pertaining to the procedure were collected. The method of sterilization was complete immersion with Cidex^®.

Results:

The instruments were substituted after 113 and 102 procedures, respectively. The first F-URS was used for a total operative time of 79 hours and 10 minutes while the second one was used for 71 hours and 25 minutes (mean 75 hours and 15 min). Procedure duration was 15 to 175 minutes (mean 58 min). The flexible instruments were used for a mean of 42 minutes per procedure (range 13–153 min). The indications for F-URS were therapeutic in 75.4% and diagnostic in 22.8% of the cases. For lower pole calculi, the stone was relocated in 65.2% and managed with the nonflexed flexible instrument 90% of the time. The most common causes of damage of F-URS were: Deflection mechanism impairment, inner sheath damage, and fiberoptic bundle breaks.

Conclusions:

Increased durability of F-URS was from a variety of factors, a key element of which was the method of sterilization, while routine use of the semirigid instrument initially further contributed significantly to increase the number of F-URS procedures, saving overall costs.

Introduction

F lexible ureterorenoscopy (F-URS) is now widely practiced as a diagnostic and therapeutic urologic procedure in modern urologic care. Technologic development of modern flexible ureterorenoscopes, with reduction in both tip and shaft diameter, has helped easier introduction into the ureter¹ (even without routine use of a ureteral access sheath). Together with improved mechanisms of deflection, the indications for F-URS have expanded, both as a diagnostic and as a therapeutic tool, in the treatment of a diverse range of upper urinary tract (UUT) pathologies (calculi, tumors, caliceal diverticuli, strictures, etc),^2

–9 thereby creating greater instrument stress with a consequential reduction in durability and ultimately driving up costs.^10,11

Several groups have studied different instruments' durability and suggested tricks to improve longevity. White and Moran (1998),¹² Afane and colleagues (2000),¹³ and more recently Monga and associates (2001 and 2005),^14,15 using different instruments, demonstrated longevity ranging 6 to 25 procedures. Pietrow and coworkers (2002)¹⁶ evaluated the performance of four new Olympus™ 7.5F ureteroscopes in a total of 109 ureteroscopic procedures under the supervision of two attending physicians. They reported an average of 27.5 uses (range 19–34) before repairs were needed. Later, Traxer and associates (2006)¹⁷ demonstrated how to increase the performance of the instruments, reaching 50 procedures with the 11278 AU1 Flex-X (Karl Storz Endoscopy, Tuttlingen, Germany).

In this study, our experience with the use of two consecutive flexible ureterorenoscopes (Flex-X, KSE) is reported, and suggestions are made as to how to improve durability further.

Materials and Methods

All F-URS procedures from a single tertiary care center between July 2009 and February 2011, with two new flexible ureterorenoscopes (11278 AU1 Flex-X, Karl Storz^™) used consecutively by two expert endourologists (LD and MDD), were chart reviewed retrospectively. The indications for F-URS were UUT pathologies (stone, urothelial cancer, intrarenal and ureteropelvic junction (UPJ) strictures, and stone-bearing symptomatic caliceal diverticula). All diagnostic and therapeutic procedures were included. Failed attempts of F-URS were also reported. Pure cases of ureteral pathology were excluded.

Data about the operative time of the entire procedure (from the introduction of the cystoscope to the final bladder catheter) and the time of the use of the flexible ureterorenoscope were recorded on a set proforma. Information about the location and size of stone/tumors, the use of accessory devices (ureteral access sheath, laser, basket), prestent placement, and nature of the damages to the two instruments were collected.

The access technique to the UUT was standardized. After passing a safety guidewire (Bentson 0.035″ Teflon-coated, floppy tipped) into the kidney by a cystoscope, the ureter was optically predilated by passing a 9.5F semirigid ureteroscope (Karl Storz Endoscopy) up to the renal pelvis with a guidewire in the working channel. The renal pelvis, upper and interpolar calices were also explored for possible lithotripsy/laser ablation/biopsy.

The flexible ureterorenoscope was introduced sequentially, over the working Bentson guidewire, to explore the remaining calices. In case of lower pole calculi, when possible, the stone was relocated with a nitinol basket into a more accessible upper or interpolar calix and later managed with the nonflexed flexible instrument or with a semirigid one. In the case of impacted lower pole stone or of a narrow infundibulum, the stone was broken in situ and then relocated.

A ureteral access sheath (12/14F, 35 cm Flexor, Cook) was used in cases where multiple reentries were necessary and also to minimize intrarenal high pressure in orothelial cancer cases.

Pressure irrigation was avoided in all cases, 20 mg furosemide was administered intravenously to minimize intrarenal reflux, and parenteral antibiotic prophylaxis was administered at anesthesia induction.

The working tools introduced into the working channel of the flexible instrument were: Holmium laser probe (200 μm, LISA laser); nitinol baskets (N-Circle 2.2F, Cook Urological); biopsy forceps (Piranha 3F, Boston Scientific; cup biopsy forceps 3.3F, Cook Urological), and hydrophilic guidewire with dual floppy end (Sensor, Boston Scientific). In three cases, a laser ureteral catheter (2F, Cook) was used to protect the inner sheath of the operative channel at the passing of the 200 μm fiber with the deflected instrument.

Endoscope cleaning and disinfection were performed by trained and experienced nurses, who all worked in the endourologic suite on a regular basis. The method of cleaning was complete immersion in a detergent agent for 20 minutes after cleaning the working channel with a syringe. The method of disinfection was a complete immersion with adequate disinfectant (Cidex^®) for 30 minutes after filling the operative channel with a syringe using the same solution. After that, the instrument was washed with complete immersion in saline for 10 minutes, and the channel was washed with syringed saline. At the end of the day, the instrument was cleaned as above, dried with soft paper, the operative channel was dried with syringed air, and it was preserved in its case.

The t and chi-square tests were used to statistically compare the results of the two series. P value was significant when <0.05.

Results

From July 2009 to February 2011, 215 F-URS procedures on 203 patients were reviewed retrospectively. The instruments were substituted after 113 and 102 procedures, respectively (mean: 107.5). Procedure mean duration was 58 minutes (range 15–175 min).

The first flexible ureterorenoscope was used for a total operative time of 79 hours and 10 minutes while the second one was used for a total time of 71 hours and 25 minutes (mean duration of the instrument: 75 hours and 15 min). The flexible instruments were used for a mean of 42 minutes per procedure (range: 13–153 min). The semirigid instrument was used for a mean of 14 minutes for procedures (range 1–40 min).

The indications for F-URS were therapeutic in 75.4% (stone in 53.5%, UUT- urothelial carcinoma (UC)/angiomas in 17.7%, strictures in 4.2%, and diagnostic in 22.8% (bilaterally in two patients, 4.1%).

Failed attempts overall necessitating stent placement were 1.8%.

The first instrument was used for 113 procedures on 104 patients, from July 2009 to May 2010. The treated cases were: Stone in 54.9%, UUT-UC/angiomas in 15%, strictures in 4.4%, and diagnostic in 20.3%. In 3.5%, ureteroscopic access to the kidney failed. The second instrument was used from May 2010 to February 2011 for 102 procedures on 99 patients. Indications were: Stone in 52%, UUT- UC/angiomas in 20.6%, strictures in 3.9%, and diagnostic in 23.5%. There were no failed attempts.

Comparing data of the pathologies from the two instruments, stone treatment (Fig. 1) was the most frequent indication for F-URS: 62 patients with the first instrument (54.9%) and 53 patients (52.0%) with the second one. There was no statistical difference between the two series (P>0.05) (Fig. 1). The comparative stone management with the two instruments is described in Table 1.

FIG. 1.

Comparison of the pathologies managed with the two instruments. UUT-UC=upper urinary tract-urothelial carcinoma.

Table 1.

Comparative Stone Management with the Two Instruments

Stones
	1 ^st instrument n°patient (%)	2 ^nd instrument n°patient (%)	mean %	P value
N° procedures	62/113 (54.9%)	53/102 (52.0%)	53.5%	0.09
Multiple	24 (38.7%)	25 (47.2%)	43.0%	0.21
Single	38 (61.3%)	28 (52.8%)	57.0%	0.03
≥1.5 cm	29 (46.8%)	25 (47.2%)	47.0%	0.42
<1.5 cm	33 (53.2%)	28 (52.8%)	53.0%	0.34
Bilateral	2 (1.6%)	–	0.8%	–
Access sheath	25 (40.3%)	14 (26.4%)	33.4%	<0.01
Prestent	6 (9.7%)	3 (5.7%)	7.7%	0.02
Renal pelvis	5 (8.0%)	3 (5.5%)	6.8%	0.12
Upper calix	11 (17.7%)	8 (15.4%)	16.6%	0.23
Interpolar calyx	14 (23.0%)	12 (21.2%)	22.1%	0.49
Lower calix	32 (51.3%)	31 (57.9%)	54.5%	0.38
Relocation	18 (56.2%)	23 (74.2%)	65.2%	0.29

In the case of a lower pole stone, relocation was possible in 65.2% of the cases and treated with the extended flexible scope 90% of the time. In the remaining 10%, the stone was treated with the semirigid scope.

UUT-UC/angiomas represented the indication for F-URS in 17 and 21 patients, respectively, corresponding to an average of 18% of all cases. The comparative UUT-UC/angiomas management with the two instruments is described in Table 2.

Table 2.

Comparative Upper Urinary Tract-Urothelial Carcinoma/Angiomas Management with the Two Instruments

Upper urinary tract-urothelial carcinoma/angiomas
	1 ^st instrument n°patient (%)	2 ^nd instrument n°patient (%)	mean %	P value
N° procedures	17/113 (15.0%)	21/102 (20.6%)	17.7%	0.16
Multiple	10 (58.8%)	12 (57.1%)	58.0%	0.54
Single	7 (41.2%)	9 (42.9%)	42.0%	0.47
≥1 cm	12 (70.6%)	12 (57.1%)	63.9%	0.07
<1 cm	5 (29.4%)	9 (42.9%)	36.1%	0.01
Bilateral	1 (5.9%)	–	3.0%	–
Access sheath	4 (23.5%)	2 (9.5%)	16.5%	<0.01
Prestent	–	2 (9.5%)	4.7%	–
Renal pelvis	6 (33.0%)	3 (12.7%)	22.8%	<0.01
Upper calix	6 (33.5%)	10 (45.2%)	39.4%	0.03
Interpolar calix	2 (7.7%)	4 (15.5%)	11.6%	0.03
Lower calix	5 (25.9%)	6 (26.6%)	26.2%	0.67

Failed attempts occurred only with the first instrument, and the causes were UPJ disease in two cases, a total ureteral substitution with an ileal loop in one case, and a double noncompliant ureter in the last case.

Discussion

In the last 20 years, there has been an incredible improvement in the design of and the accessories used for F-URS.^18,19 The smaller size of instruments and devices, together with the increased deflection ranges, has broadened the indications for using these instruments.^2

–9 Nevertheless, they still remain costly and fragile. In the last 10 years, because of poor smaller (7F–7.5F) instrument durability, all the manufactures have increased shaft size slightly to 8F to 8.5F, and this has also allowed the innovation of chip-in-the-tip digital instruments that deliver superior quality of vision.²⁰

Different authors have studied the durability of different instruments and tried to understand the mechanism of damage.^10,11 White and Moran (1998)¹² reported their results with Wolf™ 7325.17 and Storz™ 11274AA instruments: These scopes needed repair after an average of 12 procedures. These authors observed that the main cause of damage was the decline in the deflection mechanisms. Afane and associates (2000)¹³ showed the need for repair after 6 to 15 procedures (corresponding to 3 to 12.8 hours of use) in different instruments (Storz™ 11274AA, Circon™ ACMI™ AUR-7, Olympus™ URF-P3, and Wolf™ 7325.172). In this study, ureteroscopy was therapeutic in 90% to 98% of cases, and the access to the lower pole was 11% to 24%. Like White and Moran,¹² Afane and associates¹³ demonstrated that the failure of the deflection mechanism was the main reason for repair.

Monga and colleagues (2001)¹⁴ demonstrated a need for repair after 25 procedures with the ACMI DUR-8 and 6,1 procedures with the Storz Flex-X (2005)¹⁵ using it for 4 hours and 25 minutes. User and coworkers (2004)²¹ demonstrated the need of repair of six different instruments after 10 to 34 procedures. In their experience, Knudsen and colleagues (2010)²² demonstrated the need of repair after 5.3 to 18 procedures (corresponding to 1.8–10.4 hours of use) in different instruments (Olympus URF-P5, Wolf™ Viper, Gyrus ACMI™ DUR-8E, Stryker™ FlexVision U-500). All these authors agreed in observing a constant durability of different instruments, with a range of 6 to 34 procedures. A literature review summarizing instrument durability is provided in Table 3.

Table 3.

Literature Review Summary on Durability of Flexible Ureterorenoscopes

Author	Year	Instrument	N° procedures	Scope Life duration (hours)	Sterilization/disinfection
White and Moran¹²	1998	11274AA (Storz)	11,4	N/A	N/A
Afane¹³	2000	AUR7 (Storz) 11274AA (Olympus) URF-P3 (Wolf) 7325.172	6–15	3–13h	Steris
Monga¹⁴	2001	DUR8	25	12h, 9 min	Steris
McDougall²³	2001	URF-P3 (Olympus)	>11–15	>7h, 37 min, 10h, 18 min	Steris, Cidex
Pietrow¹⁶	2002	7.5F Olympus	19–34 (27.5)	N/A	N/A
User²¹	2004	DUR8, DUR8-E 11274AA, Storz, Wolf, URF-P3 (Olympus)	5–34	N/A	Steris
Monga¹⁵	2006	Olympus, Dur-D, Flex-X (Storz)	3–14	1.7–8.23h	Gas or Cidex
Carey¹¹	2006	DUR8, DUR 8 Elite, Flex-X)	25–48	N/A	Steris
Traxer¹⁷	2006	Flex-X (Storz)	50	76h, 25 min	Cidex
Knudsen²²	2010	DUR-8E, URF-P5 (Olympus), Viper (Wolf), FlexVision U-500 (Stryker)	5.3–18	1.7–10.5h	Gas

A real improvement was obtained by Traxer and associates (2006)¹⁷ who performed 50 consecutive F-URS using a single instrument (Karl Storz 11278 AU1 Flex-X). The instrument was used for a total of 76 hours, 15 minutes (with an average procedure time of 95 minutes). These authors proposed that the use of ureteral access sheaths (58% in their experience) may reduce F-URS fatigue by reducing stress on the tip of the endoscope.

In our analysis, the two instruments lasted for an average of 107.5 procedures (range 102–113) for a total time of 79 hours and 10 minutes for the first instrument and 71 hours and 25 minutes for the second (average: 75 hours and 15 min). In our experience. the mean duration of a single procedure was 58 minutes (range 15–175 min), with an average use of the flexible instrument of 42 minutes per procedure (range 13–153 min).

McDougall and colleagues (2001)²³ used a new Olympus URF/P3 flexible 7.5F ureteroscope for each of two 30-day study periods during which a single surgeon used the endoscope for a variety of UUT procedures. During the first 30-day period (group 1), the endoscope was cleaned by the endourology support team using the Steris 20 (peroxyacetic acid 35%) technique. During the second 30-day period (group 2), the endoscope was cleaned only by the surgeon using the Cidex (glutaraldehyde 2.4%). They demonstrated that the technique and number of personnel involved in the maintenance and cleaning of the flexible ureterorenoscope did not have a significant effect on the durability and function of these instruments. It was the arduous demands of the endourologic procedure that influenced the durability of these fragile endoscopes. In contrast, Abraham and coworkers (2007)²⁴ demonstrated the damage done by sterilization with Steris, compared twith immersion in Cidex: After 100 sterilizations with Steris, the instrument was unusable because of tears on the shaft and broken fiberoptics, while a similar instrument, after 100 high-level disinfections with Cidex, had only minimal adverse effect.

Our data were compared with that published by Traxer and colleagues,¹⁷ because the instruments were identical and from the same manufacturer. The percentage of therapeutic procedures was similar in both series (75.4% in our series vs 80% in the Traxer and colleagues¹⁷ experience, P>0.05), the duration of use was the same (75 hours and 15 min vs 76 hours), and the sterilization method was identical (Cidex).

Indisputably, ureteral access sheaths can help to reduce the stress at the tip of the instrument by reducing the resistance during introduction, although this increases the disposables cost. In our series, although an ureteral access sheath was deployed in only 25% vs 58% in the Traxer and associates¹⁷ experience, the routine optical predilation of the ureteral orifice and ureter using a (9.5F) semirigid ureteroscope reduced the need for higher sheath use and should have contributed to our greater instrument durability, without cost addition.

The increase in total number of procedures (107.5 procedures in our series vs 50 in Traxer and coworkers¹⁷) with a similar total instrumentation time, in our analysis may be attributable to longer duration of procedures in the Traxer and coworkers¹⁷ series (95 min vs 58 min), which may in turn be influenced by treatment of larger stones in the French series. Another possible explanation for the greater number and shorter duration of our F-URS procedures could be the routine use of the semirigid ureteroscope first. Thanks to its larger working channel and better view, it was possible to treat all renal pelvis or upper calix pathologies with larger tools (laser fiber, balistic probe, and rigid forceps) in a faster and safer way. With this instrument, the kidney could be reached in 98.2% of attempts.

The flexible instrument was used for all the procedures but only for the minimum needed time. The incidence of lower pole stone relocation before fragmentation to a more accessible calix was 65.2% in our experience (further reducing flexible instrument stress).

The purchase cost of a new fiberoptic flexible ureterorenoscope is approximately Euros 13,000.00 (about $16,450) (depending on instrument and manufacturer). Because our instrument lasted for 107 procedures, the cost per procedure was Euros 121.50 (about $154). This cost was surprisingly low when compared with the average published literature instrument life (6–50 procedures): Euros 2,166.66 – 260 (about $2,742 – $328).

The most common causes of damage were deflection mechanism impairment, inner sheath damage, and fiberoptic bundle breaks.

The factors that contributed to increased durability in our series included minimizing the work undertaken with a fully deflected instrument as much as possible, introducing laser fibers and guidewires when the instrument was straight, using a laser catheter sleeve (2F, Cook) for the 200 μm fiber with the deflected instrument (3%), and by having a low-risk sterilization method (which admittedly may not be uniformly acceptable in other units).

The limitations of this study are the lack of prospective design, comparability of pathology, and lack of comparative or randomized trials with other manufacturer's instruments to validate our findings in other tertiary referral centers.

Conclusions

The durability of the flexible ureterorenoscope with two consecutive instruments made by the same experienced operators, in the same tertiary care center, treating a range of upper tract pathologies, has been shown by this analysis.

Increased durability was because of a variety of factors as described, of which a key element was the method of sterilization, while routine use of the semirigid instrument can further contribute significantly to increase the number of procedures and to save overall costs.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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