Flexible ureteroscopy update: indications, instrumentation and technical advances

Retrograde ureteroscopy has recently gained a broadened indication for use from diagnostic to a variety of complex minimally invasive therapies. This review aims to look at the recent advances in the instrumentation and accessories, the widened indications of its use, surgical techniques and complications. With minimization of ureteroscopic instruments manufacturers are challenged to develop new, smaller and sturdier instruments that all will also survive the rigors of surgical therapy.


INTRODUCTION
Ureteroscopy is deÞ ned as retrograde instrumentation performed with an endoscope passed through the lower urinary tract directly into the ureter and calyceal system. [1] With the addition of actively deß ectable, ß exible endoscopes the indications for ureteroscopy have broadened from diagnostic to a variety of complex minimally invasive therapies. Current ureteroscopic treatments include intracorporeal lithotripsy (by far the most common), treatment of upper urinary tract urothelial malignancies, incising strictures, evaluation of ureteral trauma, and repairing ureteropelvic junction obstructions. [2,3] With improved instrumentation and incorporation of technologies such as a large endoscope working channel and active tip deß ection, the evolution of surgical techniques have broadened while the complications noted with ureteropyeloscopy have actually decreased signiÞ cantly. [4,5]

MECHANICS
The application of ß exible ureteroscopy was Þ rst reported by Marshall in 1964. A 9F fiberscope manufactured by American Cystoscope Makers (Pelham Manor, NY) was passed into the ureter to visualize an impacted ureteral calculus. Subsequently, Bagley, Huffman, and Lyon began work at the University of Chicago to develop an improved ß exible Þ beroptic ureteropyeloscope in the 1980s.
Three major design changes improved the therapeutic potential of the ß exible ureteroscope [ Figure 1].
The optical system consists of Þ beroptic light bundles created from molten glass. Each glass Þ ber is cladded with a second layer of glass of different refractive index to improve the internal reß ection, light transmission and also the durability of the endoscope. When the Þ bers are bundled randomly, they provide excellent light transmission for illumination, but no image. However, if the Þ bers are placed in a coherent fashion, the light from each Þ ber will coalesce to transmit images. Small lenses placed proximally and distally enable a telescopic effect with image magniÞ cation, increased Þ eld of view and focusing ability. A recent modiÞ cation is the splitting of the light bundle distally to enable a more central placed working channel and better distribution of light within the working Þ eld of view. [5] The deß ection mechanism of the ß exible ureteroscope permits maneuverability within the collecting system of the kidney. This deflection is usually provided by several wires running down the length of the endoscope and attached to a lever which is manually operated. Manipulating the lever will deß ect the tip. If the tip moves in the same direction of the lever, the defection is described as "intuitive"-i.e. down is down and up is up. In the past, prior to 1992, deß ection was active at the tip and secondary deß ection along the shaft was passive. To obtain lower pole access, the urologist would maximally deß ect and advance the tip of the endoscope. [6] The secondary deß ection was achieved by the endoscope passively buckling at a set designed point along the shaft. In 1992, Karl Storz (KSEA, Tuttilegan, Germany) was able to downsize the ß exible endoscope from 9.8 Fr to 7.5 Fr while maintaining the same 3.6 Fr working channel. This milestone event allowed all urologists to more easily pass the endoscope and in so doing broaden the therapeutic applications. The current instruments have continuous controlled dual deß ection with increased downward and upward deß ection up to 270 degrees, referred to as "exaggerated deß ection" in both directions. This deß ection is performed with a single more ergonomic lever as compared to the cumbersome two separate levers employed by the ACMI DUR 8 (Gyrus Inc, London, England). The radius of deß ection is also broader, thereby enabling more maneuverability and permitting placement of instruments in the lower pole. The most modern endoscopes also incorporate a shock absorbing system (a form of secondary deß ection) which is located proximal to the active deß ecting system and allows for gentle rolling of the distal end for approximately ten centimeters enabling access more deeply into the calyces. [7] The working channel permits placement under direct vision of a variety of accessories including graspers, baskets, wires and laser Þ bers through the endoscope. All current endoscopes have a channel of at least 3.6 Fr which allows the use of instruments up to 3 Fr while still permitting concurrent irrigation. The composition material of the accessory inß uences tip deß ection. For example, graspers and baskets with a shaft composed of polyamide tend to be stiffer and inhibit deß ection as compared to Teß on sheathed accessories. [8] Many ureteroscope repairs are due to damage to the working channel from malfunction or incorrect use of the holmium laser. This is often a technical issue when the Þ ber Þ ring end is located too close to the endoscope tip. The new-generation Storz endoscopes incorporate a bead-like sequence of hollow ceramic rings in the distal end of the working channel for 1.5 cm. This protects the instrument from thermal or electrocautery damage and allows the endourologist to work closer to the tumor, stricture or stone while using laser energy.

DURABILITY
White and Moran reported the need for major urteroscope repairs after only 12 endoscope usages. [9] Afane et al., demonstrated that flexible ureteroscopes from four major manufacturers required major repairs after only 15 procedures or 13 h of usage. [10] Traxer et al., from Paris performed 50 ß exible ureterosopies using the Karl Storz Flex-X ureteroscope. They evaluated the maximal active ventral and dorsal deß ection, irrigation ß ow at 100 cm H20 and number of broken optical Þ bers. The maximal ventral deß ection deteriorated from 270 degrees initially to 208 following the last procedure; the maximal dorsal deß ection decreased from 270 to 133 degrees. The irrigation ß ow at 100 cm H20 decreased from 50 to 40 after the last procedure. They concluded that the need for repair occurred less frequently with the newer generation endoscopes and when used by an experienced endourologist. [11] In general most centers can employ these instruments for approximately 50 cases between repairs with damage and breakage occurring most often during sterilization.
Irrigating ß uids are employed to clear the optical Þ eld of view and to cool the tip of energy-delivering devices. The irrigant is delivered through the same channel used for working instruments, often through a side arm adapter (Urolock -Boston ScientiÞ c, Natick Mass. and Check ß ow, Cook Urologic, Spencer, Indiana). The simplest and most cost-effective means of delivering continuous irrigant is to employ two 60 cc syringes connected to a three-way stopcock with arterial line tubing. Normal saline is the irrigation standard solution for diagnostic ureteroscopy and lithotripsy. When electrocautery is employed sorbitol or small aliquots of sterile water may be used. [12] ACCESSORIES Accessories include guide wires, stone retrieval devices, access sheaths, electrodes, laser Þ bers, biopsy forceps, etc. With regard to guide wires, the PTFE -coated stainless steel guide wire and the Zebra wire (PTFE coated with nitinol core -Boston ScientiÞ c, Natick Mass) are useful to help facilitate endoscope tip access to the ureter in routine cases. The Terumo Glide wire is particularly useful in cases of difÞ cult ureteral access. It is employed as an access guide wire and not a working guide wire. This means that the very lubricious coating is useful in bypassing an obstruction, and can facilitate ureteral catheter placement, while the slippery nature of this nitinol design frequently does not aid in placing the larger endoscope. | October-December 2008 |  [20] Several new unique guide wires are now available including the Sensor wire (Boston ScientiÞ c, Natick, Mass.). The Sensor guide wire, for example, has a smooth hydrophilic nitinol-based distal tip, a kink-resistant body made of nitinol alloy core, and PTFE-coated stainless steel jacket which adds stiffness and helps prevent endoscope buckling during endoscope placement into the ureter. This guide wire also has a ß exible proximal tip for atraumatically back loading the wire through the working channel of the ureteroscope. [13,14] The ureteral access sheaths can facilitate repeat ureteroscopic access to ureter. These sheaths range from 12-14 Fr and enable repeated passage of the ureteroscope without a guide wire. The advantages include easy endoscope placement and possible decreased intrarenal irrigant pressures. The disadvantages include over-dilation for placement, false sense of security, and potentially increased rate of ureteral stricture from prolonged use. [15]

FUTURE ADVANCES: THE DIGITAL FLEXIBLE URETEROSCOPES
Recently, flexible digital ureteroscopes have been introduced. These endoscopes have an integrated light source and distal digital chip-based camera. The distal chip camera system requires a larger outer endoscope diameter which is an issue for access, while the image quality is equivalent to ten times the pixel resolution of standard Þ ber optic endoscopes. Since these instruments do not require a separate camera head or light cord, they may potentially be more durable.
More studies are needed before concluding that these more costly additions are superior to the conventional Þ ber optic ß exible endoscopes. Early issues include digital processing of colored light, especially red light, and problems with chip stability during laser lithotripsy where the created acoustic percussions distort the digital images.

Ureteral access
The intramural ureter is the narrowest segment and can prohibit endoscope passage. Guide wires often are passed into the ureteral oriÞ ce cystoscopically and then directed into the renal pelvis with ß uoroscopic assistance. These "safety" guide wires straighten the ureter and facilitate both the dilation of obstructed segments with balloon or graduated dilators and the placement of internal stents. [17] Historically, the intramural ureter required dilation for endoscope access. Currently, the small-diameter ß exible ureteroscopes often have less than 7.5 F tip diameter, and can be passed without any formal dilation. Use of a dilator to facilitate passage of the ureteroscope beyond the intramural tunnel is recommended when the ureter is narrow or restrictive. This is common in the young male population. Otherwise, the use of such dilators or operative sheaths is optional and generally not required. [18] One access method is to employ a 10 Fr dual lumen catheter Þ rst over the initial access guide wire. This aids in both dilating the intramural ureter and in facilitating passage of a second "working" guide wire. This scheme is useful when the ureter is tortuous or J-hooked distally. The oriÞ ce can also be dilated with a balloon dilator (most commonly 12 F for access) and a second working wire passed beside. The ß exible ureteroscope is next passed over the working guide wire in a monorail fashion into the ureter and the working guide is removed. Alternatively, the smallest diameter ureteroscopes (7.5 F tipped) can be passed directly into the ureter under direct vision without guide wire assistance. Fluid irrigation facilitates ß exible ureteroscope optical visibility. Although automatic pumps are available for this purpose, hand irrigation is often preferred. [19] In a recent prospective study of 460 consecutive uppertract endoscopies at our center, "no-touch" direct access ureteroscopy (i.e. placement of the endoscope into the ureter under direct vision without the assistance of a guide wire and without dilation) was successfully performed in the majority of patients. This wireless form of ß exible ureteroscopy or "no touch technique" is technically challenging but eliminates the potential trauma, mucosal irritation and inadvertent manipulation of stones or tumors caused by guide wires and is particularly helpful when mapping the collecting system for mucosal lesions or upper tract transitional cell cancers. [20] Another access technique is to pass the tip of a guide wire through the endoscope just beyond any blockage, or kink in the ureter and then follow with the ureteroscope until it rests beyond the obstruction. This will open or straighten ureteral segments, often allowing easier passage.
Lower-pole intrarenal access performed with a ß exible ureteroscope is often challenging and commonly requires both active and passive ß exible ureteroscope deß ections.
To place the tip of the endoscope into the lower pole, the instrument must Þ rst be actively deß ected and then advanced so as to allow the shaft below to buckle. This maneuver, termed secondary deß ection, is required in 60% of traditional ß exible ureteroscopies if a complete inspection is to be attained. The increased active tip deß ection offered by new-generation flexible ureteroscopes significantly decreases the need for secondary deß ection and enhances the surgeon's ability to inspect all aspects of the renal collecting system. Fluoroscopic guidance is frequently employed to provide a road map of the intrarenal collecting system. The ß exible ureteroscope is directed from calyx to calyx, and frequently dilute contrast material is injected through the working channel of the endoscope to help ensure the entire collecting system is mapped. [21,22] If electrocautery is to be employed, special attention to the guide wire choice helps prevent intraoperative complications. If a standard stainless steel guide wire is used, electrical current may inadvertently arc to the wire during cautery use and cause excessive ureteral coagulation with subsequent Þ brosis and stricture formation. This can be prevented by using an insulated guide wire such as a Teflon-sheathed nitinol Zebra wire (Boston Scientific, Natick, Mass.).

Endoscopic lithotripsy
Endoscopic lithotripsy is the most common indication for ß exible ureteroscopy. Holmium laser energy is by far the most efÞ cient endoscopic lithotrite. The smallest diameter laser fiber (200 micron) helps facilitate complete tip deß ection and is useful when lower pole stones are being addressed. The vaporization bubble created when this laser energy is delivered in a water-based irrigant increases exponentially with larger Þ ber diameters. The 365 micron Þ ber, for example, more efÞ ciently clears stone, but the stiffer nature of this Þ ber limits its use in the intrarenal calyceal system. [23] There are a variety of schemes employed to treat intrarenal calyceal stones with the ß exible ureteroscope and laser lithotripter. One common technique is to manually move stones from a dependent calyx with a ß exible three-prong grasper or nitinol-based loop extractor like the Graspit. Once repositioned, the stones can be more efÞ ciently fragmented with a larger diameter laser Þ ber. For the largest stones the most efÞ cient technique is to core out the central component, creating mostly dust, and then reduce the periphery to small fragments 1 to 2 mm in diameter which are left to pass over time beside a ureteral stent. For smaller stones, however, multiple endoscope passes to extract fragments, with or without a sheath, may be performed.
Internal ureteral stents are associated with lower urinary tract symptomatology, which includes urinary frequency, urgency, and mild-to-moderate hematuria, which is transient. If ureteral dilation is required for ureteroscope access, and/or the endoscopic procedure is complex (large stone burden, ureteral tortuosity, etc.) a ureteral stent is placed at the end of the endoscopic procedure to ensure drainage. Ureteral stents are also useful in that they can help straighten a tortuous ureter and facilitate passive dilation which is useful in clearing stone fragments. Removal of ureteral stents is performed after a period of healing that can range from a few days to six to eight weeks, depending on the complexity of the treatment. Stents are removed most commonly in the ofÞ ce with either an attached nylon tether or cystoscopically. [24] Most ureteroscopic lithotripsies are performed as day surgery outpatient procedures. Patients are discharged on prophylactic oral antibiotics and analgesics. Anticholinergic medications and alpha-blockers may be used to minimize symptoms of frequency, urgency, and discomfort often associated with ureteral stents; however, individual patient tolerance varies. Choosing the correct stent length (based on the ureteral length) and optimal positioning help to minimize unpleasant symptoms.

Minor intraoperative complications
In general, the minor complication rate from ureteropyeloscopy has decreased based on refined technique, experience of the operators, and prompt | October-December 2008 | treatment or prevention of intraoperative problems. Prophylactic parenteral antibiotics, careful guide wire placement, minimization of excessive ureteral dilation, and postoperative ureteral stenting all impacted on the rate of postoperative problems. This, combined with better surgical training and improved instrumentation, resulted in this very positive trend.

Major intraoperative complications
The major complication rate associated with therapeutic ureteroscopy has decreased markedly and currently occurs in less than 1% of all procedures. As with the minor problems, major complications occur less frequently for basically the same reasons -better surgeon skills and improved instrumentation. However, when they do occur treatment is often more complex. In addition to major intraoperative problems, other complications that occur during upper urinary tract endoscopy may begin as minor events and, if left untreated or if addressed incorrectly, can progress to more serious conditions.
Major ureteral wall perforations occur infrequently and can be the product of a heavy-handed endoscopist and improper application of the ureteroscope. These complications are more common with the semi-rigid ureteroscopes rather than the ß exible ureteroscopes. The forceful positioning of a semi-rigid ureteroscope above the iliac vessels, particularly in young male patients, is associated with a signiÞ cant risk of ureteral wall trauma unless the collecting system is dilated or the ureter has been stented prior to endoscopy. Routine use of a double-J stent is not necessary in most patients but is recommended when unusual difÞ culty is encountered or when extensive strictures are noted. It is essential to note that if the endoscopic maneuvers are difÞ cult, the surgeon can only be rewarded with an easier time in the future if he does not push the procedure but rather places a stent and returns another day. Usually, one to two weeks of stenting greatly facilitates ureteroscopy, particularly if proximal access is desired.
Care must be taken when treating stones in the ureter. Ureteral wall perforation with stone migration into the defect can lead to formation of a stone granuloma and/or ureteral wall stricture. In addition, attempts at extracting a particularly large stone with a basket rather than fragmenting it can lead to a ureteral perforation or avulsion. The general rule is if a stone or fragment is too large to pass on its own, trying to extract it with an accessory without reducing its size with an endoscope lithotrite has inherent risk. [25] When distal ureteral avulsion is noted, ureteroneocystostomy repair can be performed, with a psoas bladder hitch if necessary to create a tension-free anastomosis. A Boari bladder wall ß ap will increase the proximal extent of the repair to the middle third of the ureter. These repairs are performed most commonly over a ureteral catheter with perianastomotic drainage. This can be performed acutely at the time of the injury or in a staged fashion after proximal percutaneous drainage is obtained at the time of the injury.
If the entire devitalized ureteral segment is inadvertently brought into the bladder, it is of no value in subsequent repair. Percutaneous renal drainage should be obtained immediately at the time of this type of ureteral injury. Subsequent therapy is based on either bowel interposition (i.e., ileal ureter) or renal auto transplantation to a pelvic position. Both procedures are complex and should be performed in a staged fashion after a period of healing Table 2.

CONCLUSION
Miniaturization of ureteroscopic instrumentation will continue, with smaller Þ ber optics, improved mechanics facilitating lower pole access, improved accessories, and new energy sources. As the instrumentation becomes smaller and more reÞ ned, it also will become more delicate. Thus, manufacturers are challenged to develop new, smaller Rajamahanty et al.: Flexible ureteroscopy -instruments