Intrarenal manipulation of flexible ureteroscopes: a comparative study

Abstract

OBJECTIVE To compare the relative ease of manipulation around a calyceal model in the hands of experienced ureteroscopists of four flexible ureteroscopes (FUs), as new‐generation FUs provide exaggerated active deflection to facilitate intrarenal manipulation. SUBJECTS AND METHODS Four FUs of <7.5 F were tested: the FlexVision U‐500 (SF) (Stryker Endoscopy, San Jose, CA, USA), the Dur‐8 Elite (D8E) (ACMI, Southborough, MA, USA), the Viper (Richard Wolf Medical Instruments, Vernon Hills, IL, USA) and the URF‐P3 (Olympus Surgical, Orangeburg, NY, USA). Eight experienced ureteroscopists, each with a minimum of 100 flexible ureteroscopies over the preceding 3 years, assessed the FUs. The Mediskills calyceal model represents a moderately hydronephrotic collecting system, with a renal pelvic width of 2 cm, infundibular widths of 1 cm and infundibular lengths of 2 cm. The middle calyx infundibular angle was 80° and the lower calyx infundibular angle was 100°. The model does not allow for significant passive secondary deflection. The surgeons manoeuvred systematically around a four‐point course, from the pelvi‐ureteric junction, to anterior lower calyx, to anterior middle calyx, to posterior lower calyx, to posterior middle calyx, touching a metal sensor with an fulguration electrode, to trigger an automated signal at each calyx. The order of FU used by each surgeon was randomized. Each surgeon performed the course twice with each FU, ending with the first FU they started with, to diminish the impact of ‘learning the course’. RESULTS There were significant differences in the mean (sd) total time for manipulation through the four‐point course, for the Viper, SF, D8E and URF‐P3, at 29 (11), 37 (23), 38 (20) and 50 (24) s, respectively (P = 0.034). The URF‐P3 took longer to reach the posterior lower pole, at 18.1 (14.5) s than the Viper, SF and D8E, at 6.3 (2.8) (P = 0.004), 6.6 (3.3) (P = 0.008) and 7.7 (4.9) (P = 0.008), respectively. The Viper was quicker to reach the posterior middle pole, at 7.3 (4.0) s, than the URF‐P3, SF and D8E, at 14.9 (13.1) (P = 0.036), 14.7 (14.3) (P = 0.056) and 12.7 (14.0) s (P = 0.115), respectively. Subjectively, six of eight endoscopists stated that the Viper was the better FU for ease of manipulation, while five of eight stated that the URF‐P3 was the most difficult. Notably, all eight endoscopists had more clinical experience with the URF‐P3 than with the other three FUs tested. CONCLUSIONS In a model of a moderately hydronephrotic kidney with long infundibulum and limited ability to perform passive secondary deflection, FUs with exaggerated active deflection outmanoeuvred the URF‐P3. The Viper was better for manipulation in the hands of experienced endoscopists.

Influence of Pyelocaliceal Anatomy on the Success of Flexible Ureteroscopic Approach

“…In a study performed by Monga and Weiland on a model of a moderately hydronephrotic kidney with long infundibulum, the flexible ureteroscopes with exaggerated active deflection permitted a much faster and easier approach of the lower pole than the endoscopes with standard deflection. 2 However, when factors associated with a poor success rate of the retrograde flexible approach (including difficult lower pole anatomy) are present, the urologist should consider other treatment alternatives. A thorough study of the literature revealed that when the influence of these anatomic characteristics was evaluated in relation to SWL outcome, despite the controversies, many authors agreed that an unfavorable anatomy significantly alters the success rates, more severely than in cases treated by retrograde flexible ureteroscopy.…”

Flexible ureterorenoscopy (URS) for lower pole calculi

“…Occasionally, despite the measures described above, lower pole access may be unsuccessful [3]. Dual active deflection or 270° active deflection ureterorenoscopes can be helpful in such cases [4]. Sometimes the neck of the calyx is too tight or the stone may not be lying in the collecting system.…”

New technology in the treatment of nephrolithiasis

“…The fact that an experienced endoscopist can overcome the limitations of the older potentially inferior ureteroscopes is, however, not sufficient proof. In fact, Monga et al [9] allowed experienced ureteroscopists accustomed to standard primary active deflection to test various flexible ureteroscopes in vitro, and the majority subjectively preferred those incorporating secondary active deflection and performed better at accessing the lower pole. Dual-deflection devices will certainly play a role in the future, but that role remains to be defined and will vary by surgeon.…”