43 Renato N. Pedro1 & Manoj Monga2 1 Faculdade de Medicina São Leopoldo Mandic, Campinas, Brazil 2 Center of Endourology and Stone Disease, The Cleveland Clinic, Cleveland, OH, USA Before the collaborative efforts between engineers and urologists spurred by the birth of endourology in the early 1980s, upper urinary tract diseases were managed through large open incisions and were associated with significant associated patient morbidity [1]. The advent of flexible and semirigid ureteropyeloscopy has lead to less invasive treatment options for the upper collecting system. Over the course of time, lead by the interaction between engineering and medicine, the instrumentation and technique of endourology has continued to be refined and improved. After induction of anesthetic, the patient is placed in a lithotomy position with the ipsilateral leg slightly extended [2]. Although recommended primarily for patients with a moderate risk of thromboembolism [3], we routinely utilize pneumatic compression boots in all patients in the lithotomy position to decrease the risk of deep venous thrombosis and decrease the risk of intracompartment pressure [4]. The C‐arm monitor, video monitor, and holmium laser machine are positioned on one side of the patient such that the surgeon’s attention to the C‐arm image, endoscopic image, and laser foot pedal are all “in line,” requiring little movement of the head but rather subtle movement of the eyes. It is helpful to utilize software that draws the fluoroscopic image into a “picture‐in‐picture” format on the endoscopic image. Typically a flat‐screen monitor mounted on a swivel arm is utilized. The C‐arm device is positioned on the other side of the patient to allow for free movement of the image intensifier from the kidney to the pelvis. On occasion, if there is uncertainty as to whether the pathology may require a percutaneous approach, the patient may be positioned in a prone‐split leg position, so that it is easy to proceed with posterior percutaneous renal access if needed [5]. The use of a safety wire is encouraged for all urological endoscopic procedures, although some authors suggest it is not needed if active stone basketing is not planned as part of the procedure [6]. Guidewires facilitate and maintain access to the upper urinary tract and may straighten an otherwise tortuous path. The ideal guidewire would require little force to bend in response to obstruction, and a large force to perforate through tissue. These properties were examined in an in vitro study with nine commercially available guidewires and the lubricous, soft‐tip nitinol Glidewire (Boston Scientific, Natick, MA, USA) was the safest wire for initial access to the ureter, as it is less likely to perforate and more likely to bend before a point of obstruction [7]. Another study has evaluated a new set of straight‐tip hydrophilic guidewires that has been recently launched in the market based on the same properties as described later and in comparison to Glidewire (Boston Scientific). The Glidewire and the EZ Glider (Olympus) required the most force to perforate the in vitro model and presented the lowest tip bending forces. Moreover, in the same study five stiff wires were also tested and the GlidewireS (Boston Scientific) required the greatest force in the perforation test and the lowest tip bending force, as did the EZ GliderS (Olympus) [8]. A standard guidewire would also have a fairly stiff midshaft to straighten the ureter and facilitate coaxial passage of other devices (e.g. sheaths, stents). It would have a floppy tip on the external end to facilitate atraumatic back‐loading of the flexible ureteroscope if needed. The Bard Sensor guidewire (Boston Scientific) is a hybrid wire that combines these components; a hydrophilic distal tip, shift shaft (nitinol core with polytetrafluoroethylene coating), and floppy proximal tip [9]. We typically utilize a 0.035 inch Olympus UltraTrack guidewire as our initial guidewire to cannulate the ureteral orifice and advance up to the level of the renal pelvis. If resistance is encountered, a 5 Fr open‐ended catheter is advanced to the level of resistance under fluoroscopic guidance and retrograde pyelography is performed to delineate the ureteral anatomy. A 0.035 inch straight‐angle hydrophilic Terumo Glidewire (Terumo Interventional Systems, Somerset, NJ, USA) is then placed through the open‐ended catheter and advanced beyond the site of obstruction. For coaxial passage of ureteral access sheaths and large caliber stents and catheters an Amplatz Superstiff in utilized to minimize the risk of wire buckling or kinking (Boston Scientific). The Orchestra (Coloplast, Humlebaek, Denmark) is a new hydrophilic guidewire that has demonstrated, in an in vitro analysis, similar safety performance while providing a stiff shaft and more lubricous coating when compared to Glidewire [10]. In conclusion, each hydrophilic guidewire has particular properties that can be translated into advantages for a specific case; therefore it is important for the endourologist to be attentive to technological advancements and performance reports. At times the ability to guide a wire past a point of particular tortuosity may prove beneficial to establish secure guidewire access. One alternative would be to utilize an angled‐tip guidewire and a torque device which attaches to the external end of the wire. Rotating the torque device reorients the tip of the wire to direct it towards the anticipated path of the lumen as outlined on retrograde pyelography. Alternative, a variety of torqueable angled catheters (Kumpe catheter, JB‐1 catheter, Cobra catheter) can be utilized to help guide the wire in the correct direction. Ureteral access sheaths (UAS) facilitate expeditious and atraumatic entry and re‐entry to the upper collecting system with the flexible ureteroscope, while eliminating the risk of buckling of the endoscope in the bladder. The use of a UAS has been demonstrated to decrease operative time and cost, minimize patient morbidity, and optimize overall success of flexible ureteroscopy [11]. Specifically, a retrospective case series has demonstrated superior stone‐free rates in a contemporary series of patients undergoing ureteroscopy with the use of an access sheath compared to no access sheath [12]. The access sheath also protects the upper urinary tract from increased peak intrarenal pressure even with irrigant fluid pressurized to 200 cmH2O, as it allows efflux of irrigant fluid through the sheath and around the ureteroscope, maintaining intrapelvic pressures below 20 cmH2O [13]. Finally, some authors have suggested that the use of a UAS decreases the risk of endoscope damage [14]. Conversely, UAS insertion has recently been associated with ureteral injuries of various magnitudes [15], endorsing the importance of knowing the characteristics of each UAS available in the market so as to choose the most appropriate one for a particular case. In vitro and randomized clinical studies have demonstrated that the Cook Flexor® sheath (Cook Urological, Bloomington, IN, USA) is superior with regards to ease of placement, instrument passage, and stone extraction [16], is more resistant to both buckling at the ureteral orifice and kinking after removal of the inner dilator [17], and has one of the largest inner diameters in the most common bending positions of straight and 30° bends, which further facilitates stone extraction [18]. Nevertheless, in a recent in vitro study, the Navigator HD (Boston Scientific) was found to be the most resistant to buckling and have the most slippery sheath when compared to other new‐generation UAS, whereas Cook Flexor sheaths were the least traumatic [19]. New UAS models have been designed, such as Re‐Trace® (Coloplast) and Cook Flexor Parallel® (Cook Urological); both can slide over a stiff guidewire placed only at the tip of the inner sheath (outside the sheath shaft). This new design allows for an easy extraction of the inner sheath without taking out the working wire, which, in turn, becomes the safety wire. Additionally, the Cook Flexor®DL (Cook Urological) UAS offers an additional 3 Fr working channel. The extra working channel can be used for irrigation, to deliver contrast, and for introduction of wires and baskets in parallel to the sheath itself. A 12/14 Fr UAS is the standard size utilized for adults, as studies have demonstrated that this internal diameter optimizes irrigant flow and intrapelvic pressures [20]. Typically a 35 cm long sheath is utilized for women and 45 cm is utilized in men if the goal is to reach the ureteropelvic junction. If the sheath does not go up the ureter, the inner dilator can be used without the outer sheath to dilate the ureter over a superstiff guidewire. If unsuccessful one might utilize a ureteral balloon (see below) through the sheath or place a ureteral stent to passively dilate the ureter. While a number of different endoscopic lithotrites, such as ultrasonic, electrohydraulic, pneumatic, and laser, have been utilized for ureteroscopic lithotripsy, the holmium laser has become established as the standard of care, due to its efficiency, versatility, and safety. In vitro analyses have demonstrated that the holmium laser fragments all stone compositions and produces smaller stone fragments than pneumatic, electrohydraulic, and pulsed‐dye (Candela) lithotripsy [21]. While electrohydraulic can cause damage even if fired from several millimeters away, holmium laser can be safely activated at a distance of 0.5–1 mm from the ureteral wall without risk of perforation as the energy is effectively absorbed in the fluid medium [22]. Holmium:YAG laser lithotripsy generates a photothermal process that leads to direct absorption of the laser energy by the stone and thermal combustion. It also creates a vaporization bubble that subsequently destabilizes and decomposes the stone [23]. It has been published in clinical trials that the stone‐free rates both at the end of the ureteroscopy and 3 months postprocedure were significantly higher for holmium than either electrohydraulic [24] or pneumatic [25] lithotripsy. Currently, dual‐pulse‐width laser lithotripsy has shown in in vitro studies to cause less stone retropulsion with the same stone fragmentation rates [26]. Laser energy is brought to the target (stones) with the aid of laser fibers, which are thin and flexible, the optimal characteristics for passing through the working channel of a flexible ureteroscope. Studies on performance and safety of commercially available holmium laser fibers demonstrated that the Dornier Lightguide 200 was the most likely of small fibers (200–273 mm) to fracture and damage a flexible ureteroscope, while the Lumenis 272 (Coherent) and the Innova Quartz 400 (Gyrus‐ACMI) were the most durable in their size class [27]. The 365 µm laser fiber is more durable and results in the best stone fragmentation efficiency [28, 29]. However, the increase in size leads to a decrease in active deflection of the flexible ureteroscope; only 7–16% of maximum deflection (−9 to −19°) is lost with the 200 µm fiber compared to 18–37% (−24 to −45°) of maximum deflection with the 365 µm fiber [30, 31]. Flexxiva® (Boston Scientific) is a newly designed ball‐tip laser fiber. Its atraumatic tip is protective of the working channel and has shown reduced insertion forces when compared to standard, flat‐tip fibers [32]. Flexxiva passes through a deflected scope without puncturing or tearing the scope coating [32]. Pneumatic lithotripsy has the advantage, especially in areas where resources are limited, of low maintenance and disposable costs. The disadvantages of pneumatic lithotripsy are the increased risk of stone migration and the inability to apply this modality through a flexible ureteroscope. Electrohydraulic lithotripsy generates a spark which results in plasma expansion at supersonic speed, propagating a hydraulic shock‐wave and cavitation bubble. Collapse of the cavitation bubble leads to a second shock‐wave, which if asymmetric leads to formation of a liquid jet. Each of these mechanisms results in stone fragmentation [33, 34]. However, the safety of the device is the primary concern, with one series reporting a 3% conversion rate to open surgery due to ureteral perforation in conjunction with a stone‐free rate of only 58% at 3 months [35]. A variety of devices have been developed to prevent stone migration during intracorporeal lithotripsy. The Stone Cone (Boston Scientific) consists of concentric coils which act to prevent proximal retropulsion of stone fragments, and it has proved to reduce the incidence of residual stone fragments >3 mm in size [36]. The 2.8 Fr Cook N‐Trap is composed of 24 interwoven nitinol wires that has been shown in ex vivo pig ureters to prevent the migration of small plastic beads as small as 1.5 mm [37]. Each device is designed to release any larger fragments as the device is withdrawn. It has been demonstrated that the Stone Cone releases the stone with a mean of 0.19 lb of force while the N‐Trap releases the stone with a mean of 0.86 lb of force, suggesting a potential safety advantage with the Stone Cone [38]. More recently, the Percsys Accordion has been launched and was proved in an in vitro comparative study to be as safe and efficient as the Cook and Boston Scientific counterparts [39]. In vitro studies have evaluated a biogel polymer that is delivered using a 3 Fr ureteral catheter above the stone to occlude the more proximal ureter. The triblock polymer of polyethylene oxide is a liquid at low temperatures and turns into a gel at body temperature.[40] Warm irrigation must be utilized during the procedure, then cold saline is instilled to liquefy the polymer at the completion of lithotripsy. Residual polymer dissolves in urine after 2 hours and is expelled [34]. In a recent randomized clinical trial, Rane et al. reported the successful use of a water‐soluble polymer (BackStop) to prevent stone migration during semirigid ureteroscopy. The study showed that this polymer was efficient in stabilizing the stone during laser or pneumatic lithotripsy; moreover, no adverse events were associated with its use compared to conventional ureterolithotripsy [41].
Ureteroscopy Working Instruments
Introduction
Patient preparation
Ureteral access
Torqueable catheters
Ureteral access sheaths
Intracorporeal lithotrite
Ureter‐occluding devices
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