What effect do different 200 μm laser fibres have on deflection and irrigation flow rates in a flexible ureterorenoscope?

Novel syphon ureteric access sheath has the potential to improve renal pressures and irrigant flow

OBJECTIVE

To describe a novel syphoning ureteric access sheath (UAS) intended for use during flexible ureterorenoscopy (URS). We aimed to assess if in vitro it could reduce intrarenal pressure (IRP) and increase irrigant flow compared to traditional UASs.

MATERIALS AND METHODS

A validated phantom kidney with fibre optic pressure sensing capabilities was used to assess the IRP. Standardised 80 cmH₂ O irrigation via a ureterorenoscope was instilled through traditional UASs (11/13 and 12/14 F) and compared to the novel 11/13-F syphoning UAS. The measured minute volume, calculated hourly flow volume, and steady state IRP were compared.

RESULTS

The traditional 11/13 and 12/14-F UASs had statistically poorer irrigant flow than the novel syphoning UAS, at 19.3 vs 29.3 mL/min (P < 0.001) and 22.7 vs 29.3 mL/min (P = 0.002), respectively. The steady state IRP was 20 mmHg for the traditional 11/13 F and 13 mmHg for the 12/14 F compared to 0 mmHg for the novel UAS.

CONCLUSION

The described novel UAS is different from traditional devices by incorporating a syphon mechanism. Our in vitro assessment demonstrates that the novel UAS holds clinical potential to reduce IRP while allowing a significant increase in irrigant flow compared to larger diameter traditional UASs.

Comparison of flexible ureteroscopy damage rates for lower pole renal stones by laser fiber type

OBJECTIVES

Laser lithotripsy, often used during ureteronephroscopy (URNS), requires the Ho:YAG optical fiber transmit energy via total internal reflection (TIR). In critical lower pole deflections, energy may refract into the cladding causing fiber failure and scope damage. New optical fiber technology aims to have increased tolerance for high degrees of flexion. We compared two brands of laser fibers with sub-300 micron cores (Sureflex, Boston Flexiva) to determine failure rates and scope repair costs.

METHODS

A retrospective cohort study comparing these two fibers for patients at a single academic institution who underwent flexible URNS with laser lithotripsy was performed from September 2013 to October 2015. Preoperative imaging was evaluated for stone burden and location. Intraoperative variables were collected, including energy use, lower pole lasering, laser fiber malfunction, and scope damage. The primary outcome was scope damage caused by laser fiber malfunction. Secondary outcome was scope repair costs. Fisher's exact test and two tailed t-tests were used.

RESULTS

Of 223 subjects, 143 met inclusion criteria, and 8 had laser fiber failure. All failures occurred with the Sureflex fiber (8 of 63, 13%) vs the Boston Flexiva fiber (0 of 80, 0%) (P < 0.01). Malfunctions occurred in 8 of 79 lower pole stone applications versus 0 of 64 non-lower pole stone laser applications (P < 0.01). No other risk factor was different between fiber cohorts, except energy setting. Scope repair cost averaged $9155 CDN, yielding an average repair cost per case of $1144 CDN for the Sureflex versus $0 for the Boston fiber (P < 0.01).

CONCLUSIONS

Both optical fibers perform well in non-lower pole locations. However, the challenge for laser fibers in lower pole URNS is to maintain TIR. Fiber failure reflects an inability to maintain reflection and is not based on energy used or stone burden. The Boston Flexiva laser fiber has fewer failures, resulting in $0 repair cost per case, compared to the Sureflex fiber in URNS with an average repair cost of $1144 CDN per case. Lasers Surg. Med. 50:798-801, 2018. © 2018 Wiley Periodicals, Inc.

Intrarenal pressure and irrigation flow with commonly used ureteric access sheaths and instruments

INTRODUCTION

Flexible ureterorenoscopy is becoming a first-line treatment for many intrarenal stones. Ureteric access sheaths are commonly used to aid access, stone removal and reduce intrarenal pressure. We evaluated the effects of two commonly used access sheaths on irrigation flow and intrarenal pressure during flexible ureterorenoscopy. We measured the effect of scope instrumentation on flow and pressure.

MATERIAL AND METHODS

We utilized a 10/12F and 12/14F, 35 cm Re-Trace™ access sheath with a FlexX2 scope in a cadaveric porcine kidney. We evaluated the effect of four Nitinol baskets (1.3F, 1.5F, 1.9F, 2.2F), three different 200 µm laser fibres and a hand-held pump. Measurements of irrigation flow and intrarenal pressure were recorded and compared between the different sized access sheaths.

RESULTS

Flow rates varied widely between access sheaths. Without instrumentation, mean flow was 17 mls/min (10/12F access sheath), versus 33 mls/min (12/14F sheath) (p <0.0001). Increasing basket size produced a gradual reduction in flow and pressure in both access sheaths. Reassuringly, pressures were low overall (<40 cm H2O). Pressures were significantly reduced when using the larger 12/14F sheath, with and without all instrumentations (p <0.0001). Hand-held pump devices have a marked effect on flow and pressure in both sheaths; with pressures rising up to 121 cm H2O with a 10/12F sheath, versus 29 cm H2O (12/14F) (p <0.0001).

CONCLUSIONS

A 12/14F access sheath offered significantly improved irrigation whilst maintaining significantly lower intrarenal pressure, when compared to a 10/12F access sheath in a cadaveric porcine model. Scope instrumentation affects irrigation flow and pressure in both sized sheaths. Furthermore, there should be caution with hand-held pump devices, especially with smaller sized sheaths, as intrarenal pressure can be very high.