Is a Safety Wire Necessary During Routine Flexible Ureteroscopy?

Introduction

T he use of flexible ureteroscopy (URS) for nephrolithiasis and other indications has been rapidly expanding. Flexible URS has become increasingly safe owing to improved technology such as miniaturization of flexible ureteroscopes, safer methods of stone fragmentation with the Holmium laser, and increased experience and skill level of urologists.

Initially, safety guidewires were maintained alongside the ureteroscope during endoscopic manipulation. The safety guidewire ensures access to the upper tract in case of a ureteral injury or excess bleeding and provides the ability to place a ureteral stent if necessary. More recently, some urologists have begun to forego using a safety guidewire for various upper tract endoscopic procedures because of more facile manipulation of the ureteroscope. The goal of this study was to examine a large series of patients who underwent flexible URS with laser lithotripsy for renal or ureteropelvic junction (UPJ) stones without an additional safety guidewire to determine the safety and feasibility of this method.

Materials and Methods

After acquiring institutional review board approval, a retrospective chart review was performed on all flexible URS cases with laser lithotripsy performed at our institution by a single surgeon (D.S.W.) from August 2003 to May 2008. Preoperative patient characteristics, radiographic stone characteristics (including stone size and location), operative findings, and postoperative outcomes were recorded. Patients with renal or UPJ stones were isolated from those with ureteral stones, as we routinely use a safety guidewire when performing URS with laser lithotripsy on any ureteral stones. Cases were then divided based on case characteristics into complicated and uncomplicated cases. Complicated cases were defined as those having concomitant obstructing ureteral stones requiring intervention, an associated encrusted ureteral stent, or difficult access secondary to a large stone burden (Steinstrasse or staghorn) or aberrant anatomy (pelvic kidney, urethral/ureteral stricture, ileal loop, suprapubic tube, and limb contractures). A safety guidewire was utilized alongside the ureteroscope in all complicated cases. However, in the uncomplicated cases an additional safety guidewire was not felt to be routinely necessary, based on previous experience, and thus not utilized.

Each procedure began with rigid cystoscopy. A 0.038-inch polytetrafluoroethylene (PTFE)-coated guidewire was passed up through a 6F open-ended ureteral catheter into the kidney. If difficulty was encountered beyond the ureteral orifice, a 0.035-inch angled glidewire was used to obtain access and later exchanged for the previously described 0.038-inch PTFE-coated guidewire. The bladder was drained and the cystoscope removed. In uncomplicated cases where the additional safety guidewire was not used, the flexible ureteroscope was passed up to the kidney over the guidewire under fluoroscopic guidance. The guidewire was removed and lithotripsy was performed with a Holmium:yttrium aluminum garnet (YAG) laser using a 200- or 400-μm fiber. At the conclusion of the procedure, a retrograde pyelogram was performed through the ureteroscope lumen and a guidewire was replaced through the ureteroscope to assist placement of a ureteral stent when necessary. If the stone burden was significant and/or there was significant ureteral manipulation during the case, a double-pigtail ureteral stent was placed.

In complicated cases where an additional safety guidewire was used, the second guidewire (i.e., safety guidewire) was inserted either with a standard ureteral access sheath or with a dual-wire introducer after first obtaining access with a guidewire (i.e., working wire). The flexible ureteroscope was inserted over the working wire, which was removed. The separate safety guidewire was left in place alongside the ureteroscope during manipulation. At the conclusion of the procedure, a ureteral stent was passed over the safety guidewire in all cases.

Results

Two hundred forty-six consecutive patients underwent flexible URS with laser lithotripsy for renal or UPJ calculi. Fifty-nine cases were bilateral, yielding a total of 305 cases for analysis. Of the 305 URS cases analyzed, 270 were considered uncomplicated. In all cases lithotripsy was performed with a Holmium:YAG laser until calculi pulverization, as is attending surgeon preference. Only two cases required moving the stone from away from a lower pole position with a basketing device. The average stone size of uncomplicated cases was 9.1 ± 3.5 mm, and the follow-up stone-free rate was 88.9% (240 of 270). All uncomplicated cases were performed without a safety guidewire, and no intraoperative complications resulted from the lack of a safety guidewire during these routine flexible URS cases, including no cases of lost access, ureteral perforation/avulsion, or need for a percutaneous nephrostomy tube. Of the uncomplicated stone cases, 54 had stones located in the UPJ. The 216 remaining stones were located within the renal pelvis and/or calyces.

Thirty-five cases were designated as complicated. Of these complicated cases, 16 had concomitant obstructing ureteral stones, 5 had an associated encrusted ureteral stent, and 14 had difficult access because of a large stone burden (Steinstrasse, staghorn) in 3 cases or aberrant anatomy (pelvic kidney, urethral/ureteral stricture, ileal loop, suprapubic tube, and limb contractures) in 11 cases (Table 1). In these complicated cases, a safety guidewire was maintained alongside the ureteroscope during lithotripsy, given the increased risk associated with the procedure. Similar to the uncomplicated URS cohort, in the complicated URS cohort there were no cases of lost access, ureteral perforation/avulsion, or need for a percutaneous nephrostomy tube. At the completion of laser lithotripsy, in both complicated and uncomplicated cases, a ureteral stent was placed at the discretion of the surgeon based on characteristics that were difficult to quantify in this study population. Of the total 246 patients, 214 (87%) had at least a single-sided ureteral stent placed at the conclusion of the case, and 100% of patients who underwent complicated URS had a ureteral stent placed.

Discussion

Early descriptions of URS advocated using a safety guidewire to straighten and stabilize the ureter, negotiate edematous or narrowed segments, and bridge a defect in the event of perforation. ¹ The approach to ureteral and renal endoscopy has changed since 1987. With the development of smaller caliber flexible ureteroscopes and the introduction of improved instrumentation, URS has evolved into a safer and more efficacious modality for the treatment of stones in all locations with increasing experience worldwide. ^2,3 Overall stone-free rates are remarkably high depending on stone location, with the vast majority of patients rendered stone free in a single procedure.

A residual 3- to 4-mm fragment is usually classified as the cutoff for successful stone-free rate after URS. Stone-free rates after URS with laser lithotripsy for renal stones range from 50% to 93% depending on stone size, location, and composition. ^{4 –7} Stone-free rates for URS with stone basketing in addition to laser lithotripsy for renal stones range from 54% to 95%. ⁸ This compares to our stone-free rate of 88.9% using laser lithotripsy alone in the uncomplicated cohort.

In all cases of URS for renal stones, we used Holmium:YAG laser lithotripsy for stone fragmentation and did not extract stones with a basket. Stone basketing potentially causes iatrogenic injury if the diameter of the stone is larger than the ureter; thus, it is our preference to not basket renal stones with preference for laser lithotripsy with a more favorable safety profile. Thus, the avoidance of stone basketing confounds our low complication rate with no cases of ureteral perforation or lost access.

In the past, other forms of lithotripsy devices were utilized, including electrohydraulic lithotripsy that creates cavitation bubbles, pneumatic lithotripters, and other laser devices (pulsed-dye or Neodymium:YAG). The safety and efficacy of Holmium:YAG laser within the urinary tract have been well documented as its tissue penetration is <0.5 mm. ^{9 –11} Thus, the chance of urothelial injury is much lower with this method of lithotripsy as opposed to those previously used.

The incidence of complications during URS has also decreased over time. Possible intraoperative complications during URS have varying degrees of severity and include the following: mucosal abrasion, false passage, extravasation, perforation, and ureteral avulsion. Older literature reports a 6.1% and 0.3% incidence of ureteral perforation and avulsion, respectively. ¹² More recently, ureteral perforation rates have diminished to <5% as a result of smaller endoscopes and increased surgeon experience. Moreover, long-term complications such as stricture formation now occur in <2% of patients. ¹³ One retrospective review investigating predictive factors for ureteroscopic complications found that increased operative time was significantly associated with ureteral perforation. Further, in this review it was surmised that there is also an increased risk of ureteral perforation with impacted stones or stones with difficult access. ¹⁴

In 2003, Moran and Bratslavsky published a limited abstract on a series of 340 consecutive ureteroscopies without a safety guidewire. They performed a comparative analysis to a cohort of patients undergoing URS at a single center with 11 urologists. They reported a stone-free rate of 96% without any complications. Failure was predictable and associated with high-grade obstruction and/or impacted ureteral calculi. Their analysis does not distinguish stone location or other confounding factors. Similar to our results, they concluded that no benefit is gained from placing a second safety guidewire and no adverse outcomes occurred with the use of a single working guidewire. ¹⁵

Another group from UC Davis retrospectively evaluated 361 patients over a 4-year period who had undergone ureteroscopic procedures without a safety guidewire. Of these, 322 procedures were performed for the management of calculi. There were no data reported regarding stone location, stone-free rate, or operative technique. They reported no intraoperative complications or need for percutaneous intervention. The article focused on data regarding ureteroscope force within the ureter with the presence and absence of a safety guidewire. They created an animal model to measure the force generated when passing a ureteroscope alongside a wire within the ureter. It was demonstrated that an increased amount of force was needed to advance the ureteroscope through the distal, mid, and proximal ureter. The conclusion was that the safety guidewire adjacent to the ureteroscope provides friction, leading to an increased force requirement necessary to introduce the ureteroscope. In addition, the presence of a safety guidewire anecdotally impedes observation, inhibits ureteroscopic manipulation, and reduces the longevity of the scope with damage from the excess stressors. ¹⁶

Without the safety guidewire creating additional friction from the PTFE coating, the ureteroscope is able to slide up and down the ureter much easier. In addition, without the safety guidewire, the torque necessary for rotation of the ureteroscope is much less and does not hinder movement. However, the deflection capabilities of these two techniques are very similar.

In our experience, a safety guidewire maintained alongside the ureteroscope during laser lithotripsy is somewhat limiting in terms of deflection and torquing capability, particularly in accessing lower pole stones. The added technical difficulty may also add time to the operative procedure. The excessive torquing used with a safety guidewire in position has, in a few cases, caused damage to the fibers within the ureteroscope, necessitating repair by the manufacturer. Although we acknowledge that this is difficult to quantify, we feel strongly that it is easier to manipulate the flexible ureteroscope without an additional safety guidewire in place. The intent of this study was not to examine deflecting and torquing capability of ureteroscopes alongside a safety guidewire, but rather to determine the safety and feasibility of a wireless technique. Therefore, if it is felt safe to proceed without a safety guidewire, it is our preference to do so.

Early endoscopes had no deflecting capability or working channel as they were designed for direct inspection of the upper urinary tract only. Since these original ureteroscopes were described, there has been a dramatic improvement in technology. Recently, ureteroscopes have become smaller in size, where at our institution we currently use a 7F-diameter scope. Fiber optics has improved, especially with the recent use of digital cameras. A dual lumen working channel allows for the use of various endoscopic instruments, in addition to instillation of irrigant to significantly aid in observation. Lastly, the advancement of deflection capabilities to the ureteroscope (both passive and active) has added much to the urologists' arsenal. The combination of these added benefits has certainly made current flexible URS much more efficacious than in previous years, and as we describe now, much safer.

Previously, urologists routinely dilated the ureter to accommodate scopes of larger caliber. In our series, ureteral dilation was performed with the use of a ureteral access sheath only in cases in which the ureteroscope did not pass easily up the ureter over a guidewire. In these cases the ureteral access sheath was only used for dilation purposes and not as a conduit for the ureteroscope to pass through. In nearly all cases, the inner cannula of the access sheath was sufficient, obviating further dilation. It is certainly possible that our lack of access-related complications may be caused by the exclusion of ureteral stones and complicated renal stones. However, among those patients excluded there were still no patients sustaining a major ureteral injury including avulsion or perforation. In addition, we have compiled a list of cases that we believe do require a safety guidewire to be maintained throughout the procedure (Table 2). In the future, we hope to conduct research evaluating the rate of ureteral strictures after endoscopy both with and without the use of a safety guidewire.

Conclusions

This study demonstrates that, in a large series of patients, a safety guidewire was not necessary for routine cases of flexible URS with laser lithotripsy on renal or UPJ stones. Particular cases with complicated anatomy, difficult access, concomitant ureteral stones, simultaneous stone basketing, or bulky stone burden still necessitate use of a safety guidewire because of increased risk of adverse outcomes.