Introduction

Before the development of ureteroscopy, upper urinary tract diseases were managed through open procedures which led to a significant morbidity rate [1]. The constant interaction of engineering and medicine leads to the development of less invasive treatment modalities and improvement in the quality of clinical care; thus, the creation of digital sensor ureteroscopes, improvement of working elements, and the advent of the holmium laser had a great impact and allowed more complex procedures to be performed endoscopically [2].

The complex and fragile nature of flexible ureteroscopes leads to issues with reliability and cost of maintenance. The introduction of digital ureteroscopes was based on the image-to-digital data conversion and light-emitting diode, which resulted in great improvement and durability of these instruments, enabled significant design improvements, and reduced the use of fiber-optic scopes [3]. Despite the improvements in durability, the fragile nature of flexible ureteroscopes still poses a major financial burden for their clinical use [3]. Most failures are attributed to iatrogenic causes such as use of accessory equipment, sterilization, or improper handling at the time of sterilization [4].

The introduction of digital ureteroscopes not only improved durability but also allowed for larger working channels, which permit superior rate of irrigation flow , the use of larger instruments, and removal of biopsy specimen through the channel [5]. Adequate irrigation flow is crucial for optimal visualization of the endoscopic field and for access to the urinary tract.

Durability of Flexible Ureteroscopes

Initial reports highlighted the excellent optical characteristics , design, and improved functions of these newly introduced digital instruments [6, 7]. However, studies evaluating and comparing the durability of new generations of ureteroscopes are limited. The durability of the ureteroscopes is related not only to the design but also to the technique of use and operator experience. Training in digital ureteroscope technique is a key component of subspecialty training in urology, mandatory for patient safety and the optimal care of instruments.

A study conducted by Sung et al. analyzed data on the characteristics of ureteroscope damage [8]. Data was obtained from the four major manufacturers (ACMI, Karl Storz, Richard Wolf, and Olympus). The frequency of repair increased with decreasing ureteroscope diameter and increasing scope length. Working channel laser burn and extreme scope deflection were major causes of damage to flexible ureteroscopes.

Afani et al. compared early generation flexible ureteroscopes and concluded that although luminosity and irrigation flow remained unchanged, there was significant deterioration (2–28%) in active deflection after the ureteroscopes were used for 6–15 uses (3–13 h) [9]. Information gained in this early study is useful because it serves as a reference point for subsequent studies. Another study did not observe any statistical significance between the durability of six flexible ureteroscopes originating from different manufacturers. Between 10 and 34 procedures were carried out with the flexible ureteroscopes before they needed major repair [10]. Carey et al. concluded that among the most important risk factors for predicting the number of uses of a ureteroscope was the age of the device and history of prior repair [4].

Traxer et al. reported on specific damage that occurred to Storz Flex X ureteroscope after 50 ureteroscopies. Maximal ventral deflection deteriorated from 270° to 208°, and maximal dorsal deflection deteriorated from 270° to 133°. There were six broken image fibers. The authors concluded that the new generation of flexible ureteroscopes needed less frequent repair, although no direct comparison was made with the previous generation of scopes [5]. Several other investigators have marked the improved durability of the recent generations of flexible ureteroscopes [11,12,13,14].

Perioperative Care of Flexible Ureteroscopes

General Considerations of Handling the Scopes

The longevity of ureteroscopes depends largely on operator skills ; therefore, training in ureteroscopy is necessary to ensure the safety of both patients and equipment [15]. Care of the small-diameter flexible ureteroscopes begins with meticulous handling. Insertion of the flexible ureteroscope should be a smooth process. The scope should be straight during insertion, and the insertion should be done over a guide wire [22]. Fluoroscopy could be very useful under a variety of circumstances: determining the nature of the obstruction, ruling out any buckling of the ureteroscope in the bladder secondary to pathology, or determining if there is enough support by the guide wire [22]. A retrograde pyelogram or inspection of the distal ureter with ureteroscope could aid in identifying the cause of obstruction. Once inserted, the ureteroscope should be straight from the urethral meatus to the lens [23]. No instruments should be passed when the tip is deflected beyond 30° [23]. The ureteroscope shaft should not be twisted, as this may damage the fiber-optic bundles [22]. The instrument should be in its own trolley and other instruments should not be placed on it [24]. Support staff should be well trained since most scope damage occurs outside of the patient, during cleaning and storage [24]. Appropriate training of the supporting staff for optimal outpatient handling of the flexible scopes could be considered equally important as intraoperative handling of the instruments by the urologists [25]. The most common damage caused by support staff is overcurling of the scope or crushing of the scope by closing the storage case on the scope shaft [8]. Training the staff extends the life of the scopes and is cheaper than repairing or replacing the ureteroscope. Moreover, regular maintenance and service contract costs are also reduced [24].

Intraoperative Care of Flexible Ureteroscopes

The active deflection unit is the most fragile part of the flexible ureteroscope. Several studies showed that the leading cause of scope damage was working with a deflected tip, occurring either by direct damage to the deflection mechanism or by the introduction of instruments during deflection [15]. The active deflection mechanism eventually wears out with repeated use, necessitating repair or replacement of the ureteroscope [9]. Several techniques for preventing damage to the scope during intraoperative care have been proposed in the literature. Ghani et al. described a technique where they evacuated the collecting system with a syringe to draw the stone closer to the scope. Moreover, they proposed the use of a nitinol basket to reposition the lower pole stones into the middle or upper calyx, which allows working with a lesser degree of deflection and enables the passage of larger laser fibers [16].

The introduction of lasers for contact lithotripsy , tissue destruction , incision, and fulguration has significantly increased the use of the flexible ureteroscope. Small diameter laser fibers allow scope deflection, while bigger diameters deliver more power. Care must be taken during the insertion of the fiber against a deflected tip as this may cause perforations or scraping of the inner lining of the working channel. Also, the laser must not be activated if the fiber tip is not advanced outside the channel. Working with maximum deflection can cause microfractures and laser firing within the channel [2].

Ureteral access sheaths are used to facilitate ureteroscopy by decreasing the intrarenal pressure, providing better irrigation flow and visibility, as well as increasing the longevity of the ureteroscopy by providing support. Moreover, the sheaths decrease the resistance and buckling of the scope in the bladder [12, 17]. Nonetheless, the scope deflection mechanism should always be out of the sheath to avoid interfering with scope flexibility and to prevent damage to the deflection mechanism (Fig. 5.1a, b). Many studies demonstrated that the use of ureteral access sheaths decreased the operative time and cost, minimized the patient morbidity, and optimized the overall success of the ureteroscopy [18]. Ureteral access sheaths should be considered if multiple passes of a ureteroscope are necessary or if the ureteroscope cannot be negotiated easily into the upper urinary tract. Injuries and long-term complications of ureteral access sheath insertion are mainly related to maneuvers of insertion and largely can be decreased by preoperative ureteric stent insertion and by avoiding forceful insertion [19, 20].

Fig. 5.1
figure 1

(a) The flexible ureteroscope has been inserted in the sheath, but its deflection mechanism remains inside it. The deflection is significantly limited, and the mechanism of deflection is under tension and could be easily damaged. (b) The deflection mechanism is out of the access sheath. The scope can deflect efficiently. Notice the radiopaque ring at the site that the deflecting distal part of the flexible ureteroscope scope is connected to the shaft of the scope. This site should always be outside the sheath in order to prevent damage to the deflection mechanism

Full size image

Most modern accessories are made of nitinol, which resists kinking and causes minimal loss of deflection. Crucial factors to avoid complications and damage to the scope include carefully selecting extraction devices, using a safety guide wire, maintaining good visualization all the time, avoiding forceful or blind manipulation, and introducing the device while the scope is straight [21].

Processing, Cleaning, and Sterilization of Flexible Ureteroscopes

A main cause of damage outside the patient is the cleaning technique. Some available cleaning techniques do not ensure instrument viability and appropriate sterilization. Thus, the method of cleaning should be based on the manufacturer’s guidelines [26]. Patient safety and optimal clearing of the instrument should be ensured by documenting and monitoring the cleaning process and sterilization. A study by McDougall et al. investigated if cleaning techniques and personal errors could affect ureteroscope failure, showing that when the processing and handling of the scopes was done by the surgeons and endourology support staff, the durability of the scopes was not affected [11]. Another study compared handling of the scope by endourology staff with handling by the central processing unit. Results showed that when the endourology staff handled the ureteroscopes, the average number of uses was 28.1 before any repair. The number of uses before repair was only 10.8 when the scopes were handled by the central unit [27]. Thus, the staff should be aware of the fragility of the ureteroscope and make every effort to prevent the onset of corrosion, pitting, and rusting [28].

Prior to each use, every new, repaired, and refurbished ureteroscope should be checked, cleaned, and sterilized by following the methods recommended by the manufacturer [29]. Precleaning is necessary to remove any debris and to make the scope safe for handling. Flushing of working channels with enzymatic detergent or water and removing all visible soil from the interior and exterior of the scope are also recommended [30].

After every use, the scope should immediately be immersed in warm water. Prior to manual cleaning, a leak test should be done. To ensure that internal channels are intact and to avoid any damage to the scope, the instrument should be sent back to the manufacturer for repair if a leak is detected [30, 31]. If no leak is found, the scope should be disassembled and cleaned of all protein material using the recommended enzymatic detergent to facilitate a biocidal process [30,31,32]. After visual inspection and cleaning, a high-level disinfection or sterilization should be performed according to the manufacturer instructions and healthcare organization regulations [31]. Care must be taken to rinse the ureteroscope and flush the channels to remove any traces of disinfectant solution [30]. Adherence to strict protocols and documentation and monitoring of the process are crucial to avoid any infectious outbreaks, damage to the scope, and compromise of staff safety.

The quality of water used for the processing has a great influence on the proper function and durability of the ureteroscope. A hard layer (lime deposits, scale) might form on the ureteroscope depending on water hardness and temperature and can sometimes be very difficult to dissolve. Cleaning solutions relying on tap water—even when using deionized water—will leave mineral residues on ureteroscopes that will not wash off completely. These factors can negatively affect the instrument’s proper function. The quality of the rinsing water for final disinfection and cleaning should be free of pathogenic microorganisms. When an instrument is rinsed in tap water, recontamination can occur [28].

Routine sterilization is recommended for initial and subsequent sterilization of all instruments. Before sterilization, the ureteroscope must be fully cleaned, with all visible organic material, blood, and cleaning solution completely removed [31]. Instruments may be sterilized in ethylene oxide (EtO), steam, STERRAD® sterilization systems, or STERIS® Amsco V-PRO® sterilization systems. Sterilization is highly recommended for “critical” instruments to be used for hysteroscopy, neuroendoscopy, laparoscopy, or arthroscopy. High-level disinfection is recommended for “semi-critical” instruments which come into contact only with intact mucous membranes or non-intact skin [31].

Single-Use Ureteroscopes

Flexible ureteroscopy (fURS) has evolved to be the most used modality for surgical treatment of renal stones over the past 15 years [33]. Despite technological advances, the durability of flexible ureteroscopes is still a major concern. Due to limited durability and the relatively high cost of repair, the multiuse (reusable) ureteroscope continues to be a significant financial obstacle to initiating flexible ureteroscopy programs worldwide. Moreover, the maintenance, processing, and sterilization of flexible ureteroscopes lead to significant costs.

Flexible ureteroscope repair has been clearly stated in the literature as a significant cost parameter in several studies [37, 38]. Knudsen et al. showed that 46–59% of the cost of a flexible ureteroscopy program results from ureteroscope repairs [34]. Landman et al. evaluated flexible ureteroscopes from different manufacturers and calculated the overall costs associated with the use of each of the ureteroscopes for 25, 50, 75, and 100 cases during the 1st year (while under warranty) and with subsequent use. They concluded that 70% of the major ureteroscope repairs may result from operator-induced damage [35]. When the newer digital scopes were evaluated, the investigators observed an average of 12 uses before the need to repair the digital scopes [36]. In an attempt to address costly issues with durability and need for repairs, the single-use disposable ureteroscope was introduced; these scopes have to withstand only one case and do not require any repair or maintenance.

The LithoVue (Boston Scientific, Marlborough, MA) was the first disposable ureteroscope introduced on the market. The scope was shown to be comparable to conventional scopes in terms of visibility and manipulation in a cadaveric study [39]. Usawachintachit et al. reported the clinical outcomes between two randomized groups of patients undergoing flexible ureteroscopy for upper urinary tract pathology. The first group underwent surgery utilizing LithoVue, and the second group used reusable fiber-optic flexible ureteroscopes. LithoVue was related to an average 15.5-min reduction in operating room time and a 12.6% reduction in complications. Instrument failures were similar between LithoVue and the reusable flexible ureteroscopes [40]. Similar results showing the efficacy of single-use flexible ureteroscopes , including scopes other than LithoVue, have been published and suggest that the single-use flexible ureteroscopes could be a promising alternative to reusable flexible ureteroscopes without compromising the clinical outcome of fURS [41]. Nonetheless, the purchase cost of these scopes remains high and represents a limiting factor for their acceptance. However, recent economic studies calculating the cost of purchase, repair, maintenance, and sterilization showed that the single-use scopes could be considered more cost-effective in specific clinical settings [42, 43].

Conclusion

The clinical use of flexible ureteroscopes requires training of and care by surgeons as well as support personnel related to the maintenance, cleaning, storage, and sterilization of these instruments. The repair costs of these instruments are high and may represent a significant financial burden. The use of single-use flexible ureteroscopes may be cost-effective in some clinical settings by avoiding the need for maintenance and repair.