Locked Deflection During Flexible Ureteroscopy: Incidence and Elucidation of the Mechanism of an Underreported Complication

Introduction

With technologic advances in ureteroscopic design, flexible ureteroscopy (URS) is commonly performed with an established safety profile and has allowed urologists to achieve almost complete retrograde access to the collecting system with minimal morbidity. Ureteroscopic complication rates are well defined and relatively low in experienced centers. ^{1 –4} We encountered a case of locked deflection of a flexible ureteroscope while in the renal pelvis of a patient undergoing ureteroscopic surveillance for upper tract urothelial carcinoma (UTUC). This inspired us to critically examine the potential mechanisms for this seemingly rare complication of flexible ureteroscopy that has only been reported once previously in the literature. ⁵

At our institution, an 81-year-old gentleman with a history of low-grade, left UTUC presented for routine ureteroscopic surveillance. Retrograde pyelography was performed that revealed a stenotic upper pole infundibulum necessitating balloon dilation to allow for access and complete inspection of the collecting system. A conventional fiberoptic flexible ureteroscope with bidirectional deflection was advanced into the left collecting system without difficulty. A 0.038-inch safety wire was present. The left upper pole infundibulum was accessed with gentle pressure. The ureteroscope was fully engaged in downward deflection in the dilated, peripheral calix and remained fully deflected on withdrawal from the calix through the stenotic infundibulum into the renal pelvis (Fig. 1). In retrospect, this was an unintentional maneuver at the time.

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FIG. 1.

(A) Flexible ureteroscope retroflexed in upper pole calix after balloon dilation of stenotic infundibulum. (B) Flexible ureteroscope pulled through stenotic infundibulum while maximally deflected. (C) Ureteroscope with locked deflection within the confines of the renal pelvis.

The ureteroscope was then unable to be straightened into a neutral position with manual deflection while in the renal pelvis (Fig. 2). The active deflection mechanism was locked with the flexible ureteroscope in complete downward deflection despite manipulation of the thumb lever. Given the exaggerated degree of deflection, no wire of any type could be placed completely through the working channel, including a double-floppy tip super-stiff wire. Attempts were made to place a 10F dual lumen catheter parallel to the flexible ureteroscope, but the ureter was not accommodating. Ultimately, an 8F coaxial dilator over the 0.038-inch safety guidewire was placed from below, parallel to the ureteroscope. The rationale for this maneuver was to use the coaxial dilator as a point of resistance well above the ureteropelvic junction (UPJ) by which to manually straighten the deflected scope with gentle downward pressure. In reality, this is difficult to achieve, given the deflected ureteroscope would have to be perfectly aligned to “catch” the tip of the coaxial dilator and not slip during downward retraction of the ureteroscope in efforts to manually straighten. Rather, in this case, the deflected ureteroscope tip came in contact with the medial aspect of the renal pelvis well above the UPJ, thus avoiding the most potentially vulnerable position for ureteral avulsion, in this scenario, with downward retraction of the flexible ureteroscope. This action resulted in the flexible ureteroscope becoming straight enough to safely remove completely intact. Subsequent retrograde pyelography delineated no extravasation. A new flexible ureteroscope was used to evaluate the ureteral surface, which was completely intact. We noted a small “divot” in the medial aspect of the renal pelvis about the same size of the ureteroscope tip, a few centimeters superior to the UPJ. A stent was left, and the patient did well postoperatively with no observed clinical complications.

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FIG. 2.

Flexible ureteroscope in locked downward deflection within confines of renal pelvis, unable to be removed primarily from the patient. Safety wire is in position. Color image available online at www.liebertpub.com/end

Close inspection of the ureteroscope in question was performed with a third party repair service. A significantly bent control cable was noted on the inner bend radius of the flexible ureteroscope (Fig. 3). In addition, damage was noted on the inner bend radius of the bending section on the distal aspect of the flexible ureteroscope between deflection rings (Fig. 4). Taking this information together with close review of all the fluoroscopic images saved during the case led us to the mechanism for locked deflection. The withdrawing of a completely deflected flexible ureteroscope through a stenotic infundibulum resulted in a severely bent control cable leading to the inability to straighten the ureteroscope. At the time of the procedure, this mechanism was not apparent to the operators but was later appreciated after careful review of the case. Given the potential for a seriously negative outcome, we sought to identify other cases of locked deflection in the literature and among members of the Endourological Society to better define the incidence of this problem, elucidate possible mechanisms, and propose potential solutions.

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FIG. 3.

Inspection reveals kink in control cable (angulation wire) of inner bend radius of the flexible ureteroscope. Color image available online at www.liebertpub.com/end

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FIG. 4.

Magnified view of distal portion of flexible ureteroscope demonstrates damage at the bending section of inner bend radius. Color image available online at www.liebertpub.com/end

Materials and Methods

An anonymous online survey was devised and distributed via e-mail to all active members of the Endourological Society. A total of 2424 members were surveyed, and 250 responses were obtained. Study participants were asked to respond to a series of nine closed format and free text questions regarding indication for ureteroscopy, type of ureteroscope, etiology of equipment malfunction, adverse patient outcomes, and incident reporting (Appendix 1; supplementary data are available online at www.liebertpub.com/end). All responses were blinded and tabulated by a commercially available Internet-based survey host (surveymonkey.com). The survey was circulated for 6 weeks, and results were collected electronically and evaluated. No compensation was offered to participants. In an effort to account for all possibly reported cases of locked deflection, we also searched the Manufacturer and User Facility Device Experience (MAUDE) database using key words “ureteroscopy, death, injury, and malfunction.” ⁶

Results

Completed surveys were obtained from 250/2424 (10.3%) of those polled. Locked deflection was noted by 8/250 (3.2%) of those who responded. The indication for URS was nephrolithiasis in 6/8 (75%) and upper tract neoplasm surveillance and treatment in 2/8 (25%). Retrograde manipulation was used to achieve successful removal of a locked flexible ureteroscope in 4/8 (50%) patients. An 8F coaxial dilator was used in one case as described above while another respondent reported, “just pulling hard.” The other two cases of successful retrograde removal did not specify a technique. A percutaneous approach was needed in 3/8 (37.5%) patients experiencing locked deflection. Open surgery was necessary in one case because of ureteral avulsion noted with removal of the flexible ureteroscope.

The type of flexible ureteroscope reported in locked deflection included a conventional fiberoptic scope with bidirectional deflection (170–180 degrees) in 4/8 (50%) and conventional fiberoptic scope with bidirectional deflection (170–180 degrees) and active secondary deflection in 4/8 (50%) patients. No fiberoptic scopes with exaggerated deflection (270 degrees) were noted to demonstrate locked deflection among respondents nor were any digital flexible ureteroscopes implicated. Respondents perceived the etiology of ureteroscope malfunction to be improper processing and maintenance of the scope in 3/8 (37.5%), while overuse of the ureteroscope was suggested in 3/8 (37.5%). Only 2/8 (25%) of those urologists experiencing locked deflection attributed it to improper surgical technique. The event was disclosed to patients in 4/8 (50%), hospitals in 3/8 (37.5%), and the Food and Drug Administration (FDA) in 0/8 patients. Among those found to report locked deflection, the vast majority (7/8) either did not get an explanation as to the mechanism of locked defection or did not answer that question on our survey.

Review of the MAUDE database revealed one additional case of locked deflection of a flexible ureteroscope resulting in ureteral avulsion and necessitating a left ureteral re-implant. The event description details that the flexible ureteroscope, while present in the ureter, was deflected and could not be straightened even with attempted placement of a wire through the working channel. Despite trying to remove the ureteroscope with gentle pressure, an injury to the ureter was encountered necessitating immediate ureteroneocystotomy. No mechanism was offered in the event description for this case. Review of the literature identified one published report of locked deflection of a flexible ureteroscope in 2004 in which the surgeons needed to perform an open ureterotomy through a Gibson incision to extract the flexible ureteroscope. ⁵

Discussion

Most complications during flexible URS are not directly related to the performance characteristics of the ureteroscope itself. If a flexible ureteroscope is unable to deflect or if visualization becomes impaired for whatever reason, or the working channel does not support placement of instruments, then the endoscope is usually simply removed and exchanged. These scenarios almost uniformly have no direct bearing to patient outcome as long as a viable replacement ureteroscope is available. A notable exception to this statement is a situation in which a flexible ureteroscope becomes locked in extreme deflection and is unable to be removed safely from the patient.

Locked deflection of a flexible ureteroscope has only been reported in the literature once previously. ⁵ In 2004, Anderson and associates ⁵ described a case in which a flexible ureteroscope was used to examine the lower pole of a kidney during nephrolithiasis treatment. Active and passive deflections were used, and an exaggerated retroflexion of the distal shaft of the flexible ureteroscope was encountered and resulted in locked deflection. Advancement and withdrawing of the ureteroscope did not straighten it, and wire placement through the working channel was not successful. The handle of the flexible ureteroscope was cut with orthopedic wire cutters, which still failed to release the locked deflection mechanism. Ultimately, a Gibson incision was needed to straighten the ureteroscope by way of an open ureterotomy. Postoperative examination of the flexible ureteroscope demonstrated a problematic deflection ring in its distal portion that resulted in control cables that were unable to work in opposition, thus being responsible for the locked deflection according to the authors. This was noted despite normal preoperative evaluation of the flexible ureteroscope by the surgeons.

Close examination of our flexible ureteroscope demonstrated a kinked deflection cable that was thought to result from withdrawing the deflected ureteroscope through an indurated, stenotic upper pole infundibulum. Internal review of our case revealed that this “withdrawing” of the deflected ureteroscope was not an intentional maneuver and clearly is an example of improper surgical technique during flexible ureteroscopy. This complication directly occurred because the operator pulled the fully deflected flexible ureteroscope out of the dilated upper pole calix, through the stenotic infundibulum, and did so unknowingly. To avoid this potentially complicating maneuver, the surgeon should always be keenly aware of the position of the flexible ureteroscope, especially when it is proximal to a more distally located intrarenal stricture—in this case, a stenotic infundibulum that had just been dilated by a balloon. When performing flexible ureteroscopy in a situation like this, great care should be taken to fully appreciate the position of the flexible ureteroscope within the confines of the intrarenal collecting system using ample fluoroscopic guidance as one proceeds. Not surprisingly, this complication may be encountered more often in academic institutions where residents are learning how to perform these procedures.

Fortunately, we were able to remove the ureteroscope with conservative retrograde techniques with no unfavorable consequences to the patient. Despite our success in dealing with this case of locked deflection, we acknowledge there is no guarantee that our results could necessarily be reproduced safely. It should be noted that a risk of ureteral injury still exists in any form of retrograde manipulation in this situation. The best course of action when locked deflection is encountered is not clear and will need the future efforts of both endourologists and manufacturers to determine.

According to our web-based survey, an additional case of locked deflection during flexible ureteroscopy needed an open incision for resolution. The respondent described a ureteral avulsion had been encountered while trying to remove the flexible ureteroscope. It was not specified by the respondent whether the patient needed a reconstruction or nephrectomy. Review of the MAUDE database revealed yet another case of locked deflection of a flexible ureteroscope resulting in ureteral avulsion and necessitating a left ureteral re-implant. The event description from 2011 did not mention the indication for flexible ureteroscopy but details that the flexible ureteroscope was locked in deflection while in the ureter. The endoscope could not be straightened even with attempted placement of a wire through the ureteroscope working channel. The urologist removed the ureteroscope with gentle pressure but then immediately diagnosed a ureteral injury necessitating ureteroneocystotomy. No explanation by the manufacturer or third party repair service was available for this case, and therefore the mechanism for this event is unfortunately unknown.

Therefore, taking into account the published literature, our Internet survey, and the MAUDE database, we have identified at least three cases in which an open incision was needed to either remove a flexible ureteroscope in locked deflection or reconstruct a ureteral avulsion caused directly by removal of a locked flexible ureteroscope. Truly, locked deflection of a flexible ureteroscope should be considered a risk factor for ureteral avulsion. In general, ureteral avulsion has been described in 0.1% or less in large series of ureteroscopy, ^{1 –4,7} which has traditionally been thought to be secondary to removing excessively large stone fragments down a relatively narrow ureter. ^1,8 “Scabbard” or two point ureteral avulsions have been described in which a ureteral avulsion at both the proximal and distal ureter occur simultaneously. ⁹ This very rare complication is seen only in use of semirigid ureteroscopes in which the larger diameter proximal portion of the instrument gets tightly wedged or impacted in the distal intramural ureter. On retraction of the instrument, the avulsed ureter is found around the semirigid ureteroscope much like a scabbard on a sword.

Of those eight cases of locked deflection reported in our survey, four (50%) were resolved with conservative retrograde techniques while one needed an open incision. In the remaining three cases, removal was by way of a percutaneous route. Unfortunately, we did not gather from the survey whether any of these three cases occurred during antegrade use of a flexible ureteroscope, but we suspect at least one did, in a case that admittedly was not “reported to the patient.” It is not difficult to appreciate that with rigorous antegrade manipulation of a flexible ureteroscope, especially in a percutaneous case in which bleeding could impair direct visualization, locked deflection could occur via mechanisms similar to our described case.

Taking our survey results together with the case report of Anderson and colleagues ⁵ and the MAUDE database, we can account for at least 10 reported cases of locked deflection during flexible ureteroscopy. Although our survey was not designed to accurately gauge the true incidence of locked deflection, it can be estimated based on past reports of Internet surveys of Endourological Society members who routinely perform flexible ureteroscopy. In 2011, such a survey was conducted of members of the Endourological Society concerning hand problems in those regularly performing flexible ureteroscopy. ¹⁰ In that study, 122 endourologists responded of 600 polled. The average number of flexible ureteroscopies performed was 4.5 per week, and the average time in practice for those endourologists were 13 years. That equates to approximately 3042 flexible ureteroscopies performed over an average career in those who responded. In our survey, 250 urologists responded and 8 reported locked deflection. Therefore, of a potential 760,500 ureteroscopies theoretically performed by this group of 250 endourologists, there were 8 reports of locked deflection reported, thus making the incidence of locked deflection 1 in about every 100,000 flexible ureteroscopies performed.

Nevertheless, given that fewer than 50% of these cases of locked deflection (4/10) could be managed with conservative retrograde techniques, this admittedly rare complication needs to be anticipated by endourologists. In our study, the predominantly perceived etiologies for locked deflection were improper processing and maintenance of the scope as well as overuse resulting in instrument malfunction. Two of the cases, including ours, were attributed to improper surgical technique resulting in locked deflection, however. Endourologists in teaching institutions should be mindful of the mechanism responsible for locked deflection in our case. It should be stressed to trainees that blind maneuvering of a flexible ureteroscope can have unfavorable consequences as we have seen in the case of withdrawing a completely deflected flexible ureteroscope through a stenotic infundibulum.

The role of improper endoscope maintenance or overuse is less clear as it pertains to this complication. As endoscopic surgeons, the responsibility is ours to thoroughly examine the condition of a flexible ureteroscope to document any performance issues and decide when the ureteroscope is safe to be used. Interestingly, all 10 flexible ureteroscopes identified with locked deflection were earlier generation models as best determined by our survey. All, including the previously reported flexible ureteroscope, ⁵ as well as that in the MAUDE database were conventional fiberoptic ureteroscopes with or without active secondary deflection. There were no digital ureteroscopes or fiberoptic ureteroscopes with exaggerated (270 degree) deflection implicated. The reasons for this observation are not clear. It may simply be a product of the earlier generation endoscopes being used by more urologists for more cases over time that resulted in the trend. Manufacturers will note, however, that these older ureteroscopes do not have the ability to be leak tested and therefore may be more susceptible to fluid damage by irrigation or sterilization procedures over time. We found this to be the case with our flexible ureteroscope on inspection, but it did not seem to be the inciting event that caused locked deflection.

Finally, the outcomes of this survey must be interpreted within the confines of the study limitations. The retrospective nature of this survey is subject to recall bias. Our questionnaire is designed as an open-ended, subjective surrogate for determining the incidence and outcomes of locked deflection in flexible URS and has not been externally validated. Nevertheless, this study has made the important observation that locked deflection during flexible URS is underreported formally and should be reported by the urologist to the patient, hospital, MAUDE database (FDA), and the manufacturer or third party repair service. Only in this manner can the mechanism for locked deflection be better understood and avoided.

Conclusion

Locked deflection of a flexible ureteroscope is rare but also underreported. Surgical technique plays a role in at least some of these cases, and blind maneuvering of a flexible ureteroscope within the intrarenal collecting system, especially in the presence of a stenotic infundibulum, should be anticipated and avoided. The best course of action when locked deflection is encountered is not clear and will require the future efforts of both endourologists and manufacturers to determine.