Guidewires are a mainstay of endourologic procedures, as they provide safe access to the urinary tract and allow the passage of catheters and stents [1]. The development of guidewires in urology began with the application of angiographic tools in urologic endoscopy. Fritzche et al. reported the use of angiographic guidewires in 7 patients with ureteral obstruction in 1981 [2]. The authors noted in this study that their methods allow the “placement of angiographic guide wires and catheters past ureteral obstacles when standard urological retrograde procedures are not feasible technically.” The transvesical approach was described as where a 6Fr open-ended polyethylene catheter was placed at the ureterovesical junction and followed by advancing a 0.035 in. diameter guide wire [2]. The authors noted several advantages of the angiographic catheters and wires that allowed their urological application. The smaller diameter floppy tip reduced the risk of ureteral injury. A curve could be applied to the wire to facilitate manipulation and a wide range of shapes and sizes available for angiography allowed the urologist to attach a stone basket to the catheter for multiple passages through the level of obstruction [2]. Advances over subsequent years created specialized categories of guidewires which allowed the urologist to select the most appropriate tool for a given circumstance. These wires include hydrophilic straight and angled guidewires (used for bypassing more difficult obstructions or for the tortuous ureter), the hybrid wires (wires with a hydrophilic distal tip for bypassing obstructing stones and a nitinol core which is kink resistant to be used as a working wire) and stiffer wires such as Amplatz extra stiff (used to straighten ureter or for stabilization when passing dilating catheters and access sheaths) [1, 3]. More recent studies have evaluated the mechanical characteristics and performance elements of guidewires, including tip bending, resistance, pull force, shaft bending resistance, tip puncture force, shaft stiffness, and lubricity [1, 4]. The authors corroborated that hybrid wires offer the combination of the hydrophilic tip and stiffer shaft than standard wires, while the extra stiff wires may be best-suited for placement of ureteral access sheaths or larger stents. Interestingly they also noted that “brand name” guidewires designed for the same purposes may differ from one manufacturer to the next.

There has been some controversy in the literature regarding the use of safety wires during either semi-rigid or flexible ureteroscopy. The safety wire, positioned alongside the ureteroscope during endoscopic manipulation, maintains ureteral access to the upper tract and facilitates stent placement in the case of ureteral injury or bleeding which obscures the surgeon’s field of view. Proponents of the safety wire feel that in extreme cases and unanticipated intraoperative complications, the use safety wire will decrease the rate of nephrostomy tube placement or other complication by allowing allowing for safe placement of a stent. Early ureteroscopy series originating from the mid 1980s consistently advocated for the routine use of safety wire for these reasons [5, 6]. However, more recent studies have called this dogma into question within the last decade. Advocates for the elimination of the safety wire from routine semi-rigid and flexible ureteroscopy argue that with the advent of improved optics, smaller more maneuverable ureteroscopes, and advancements in procedure technique allow the urologist to safely perform the procedure without a the safety wire [7–10]. Although the aforementioned series have demonstrated the feasibility of omitting the safety wire during ureteroscopy, it is still commonly used in practice by many [11].

During the first successful ureteroscopic evaluations of the upper urinary tract, Takayasu and Aso observed that the major challenge was the insertion of the scope into the ureter. To solve this problem, they introduced the concept of the ureteral access sheath (UAS) in 1974—they reported a guide tube made of Teflon that allowed the passage of the ureteroscope to the upper tract [12]. In a subsequent study which occurred during an 18-month period from 1984–1985, Newman et al. described a novel ureteral access sheath dilator system in 1985 and subsequently described a series of 43 procedures during which a ureteral access sheath set was used [13, 14]. They demonstrated a 51% stone free rate, 92% rate of successful ureteral stricture dilation, and 88% success rate of diagnostic evaluation of upper tract filling defects [13, 14]. Ureteral perforation due to access sheath placement/dilation were observed in 18% of procedures. The “peel-away” introducer sheath was first reported in 1987 by Rich et al.—this was a 60 cm sheath available in sizes ranging from 8 to 18 FR that was placed over a 0.038 in. guidewire. The sheath included two knobs which were used to peel the sheath and adjust to the appropriate length for the procedure. The authors reported use of this sheath for retrograde and antegrade stone basket extraction, flushing stones into the renal pelvis, retrograde stent placement, and catheterization of tortuous ureters [15]. Though early reported complications of ureteral access sheaths limited their widespread adoption, a renewed interest in these devices has occurred with the newer generation of access sheaths. First described by Kourambas et al., in 2001, the latest generation of ureteral access sheaths had an impregnated wire and hydrophilic coating, facilitating safer insertion [11, 16]. In their 2001 study, the authors randomized 59 patients to semi-rigid or flexible ureteroscopy with or without a ureteral access sheath and reported that routine use of ureteral access sheath was associated with decreased operative time and cost without an increase in complication rate. In the ensuing 3 years, additional studies on these devices noted that ureteral access sheaths decreased renal pelvis pressures during ureteroscopy (which may decrease risk of postoperative pain and infection) and also increased the time between repairs of flexible ureteroscopes due to minimizing ureteroscope damage [17–19]. In 2003, Delvecchio et al. reported long-term follow up of patients who had undergone ureteroscopy with UAS with a stricture rate of 1.4% which suggests that the use of UAS does not increase the risk of stricture development compared with ureteroscopy performed without a sheath [20]. Most recently, the CROES Ureteroscopy Global Study, a multicenter study of the use of ureteral access sheath evaluated 2239 patients treated with ureteroscopy (67% of whom had an access sheath used during ureteroscopy)—there were no observed differences in stone free rate or ureteral trauma, but UAS were associated with a 50% reduction in sepsis after ureteroscopy (4.7% sepsis rate in patients in whom UAS was used compared with 9% for no UAS) [21]. A 2014 survey of the Endourological Society with 414 respondents from 44 countries noted that 58% of surgeons routinely use a UAS for every flexible ureteroscopy procedure [22].

The initial description of a stone retrieval device was the Davis Stone extractor , described in 1953 by Thomas A. Davis [23]. This device, developed from a 5Fr ureteral catheter incorporating a monofilament Nylon thread, was used for extraction of distal ureteral stones smaller than 0.5 cm [23–25]. Nearly 15 years later, Constantian reported a success rate of 88% in a 10 year series of procedures which incorporated the Davis Stone Extractor [24]. In 1982 Enrico Dormia reported the use of the Dormia or helical basket in patients with proximal ureteral stones [26]. Under fluoroscopic guidance, a six-crossed or a three-crossed spiral basket (chosen based on stone size) was passed through a cystoscope and into the ureter. The helical design of this basket allowed engaging of the stone with rotational movement of the device after placing the basket in a proximal position. Dormia reported a 94% success rate for stone removal [26, 27]. The ensuing decade saw the development and popularization of the Segura Basket , a flat-wire, non-helical device. The design allowed for improvement engagement of the stone and was additionally used for ureteroscopic removal of papillary tumors of the upper urinary tract [27]. With the advent and popularization of flexible ureteroscopy came the need for a basket which did not significantly limit the flexibility of the endoscope—this led the popularization of the nitinol basket which is still commonly used today [28, 29]. Nitinol baskets caused minimal restriction of endoscope deflection (compared with baskets made of other materials) and the tipless nitinol basket configuration allowed for the extraction of stones with minimal trauma to the renal papilla [30].

With the popularization of ureteroscopic treatment for ureteral stones, stone migration of ureteral calculi to the upper ureter or kidney during ureteroscopy was considered an intraoperative challenge. Several measures such as fragmenting the stone within the basket, change in irrigation pressure and changes in patient position were unsuccessful to control migrating stones. As a solution, Dretler developed, in 2000, the “balloon on a wire” device. A flexible wire tip wire and a balloon that could be distended up to 12Fr and was placed alongside of the safety wire. The device was placed above the stone, which could be approached either by a semirigid or a flexible ureteroscope between the two wires [31]. This was followed by the Dretler Stone Cone, a tapered cone housed inside a catheter which could be advanced to form a spiral “backstop” to prevent cephalad migration of stones during fragmentation [32]. Several other devices were developed, each with a different mechanism of preventing stone migration (a “net” shaped backstop, an “accordion” shaped backstop, and a wireless thermosensitive polymer) and studies have demonstrated that each device prevents unwanted migration of stones during fragmentation [33–36]. However, their incorporation into routine ureteroscopy has been far less common than stone baskets.