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

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.

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.

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).

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.