Presented by: Nitin Sharma MD
University of Rochester Medical Center

Introduction

Recently TFL has been introduced in the urologist’s armamentarium and many ex-vivo studies have shown good dusting capabilities of TFL. None of the studies have actually evaluated ideal dusting settings for TFL. The objective of our study was to evaluate the results of intracorporeal lithotripsy of renal stone using TFL at a fixed setting of 0.5J and 70Hz.

Materials

145 Patients diagnosed with renal stones were prospectively enrolled for either ureteroscopy or Mini-Percutaneous nephrolitholtripsy (PCNL), based on stone size. All patients underwent laser lithotripsy using TFL (Fiber Dust^®, Quanta) at a fixed setting of 0.5J and 70 Hz irrespective of stone size or composition from May 2022 till January. Basic demographic information, stone characteristics, Total laser time (TLT) (Laser on till off time) and laser lithotripsy time (LLT) (Time laser pedal is actually pressed), and postoperative outcomes were evaluated. Ablation speed (Ratio of stone volume and laser lithotripsy time) and ablation efficiency (Ratio of Total energy used and stone volume) were also calculated.

Results

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145 patients with renal calculi > 10 mm in size were included in the study with a median age of 55 years.  140 patients underwent ureteroscopy and 5 underwent Mini-PCNL.  All stones were dusted at the fixed settings of 500mJ and 70 Hz. Mean laser ablation speed and ablation efficiency were 4.23 mm³/sec and 0.024 J/mm³ respectively. During ureteroscopy, these settings were able to achieve very fine stone dust (fragment size less than 200 microns laser fiber) by using the painting technique by continuously moving the laser fiber over the stone surface and firing from a distance. During Mini-PCNL using these settings, we were able to achieve fragments of size 3-4 mm by avoiding movement of laser fiber using the contact technique and stopping lithotripsy once stone fragments reach 4 mm size, which were then evacuated using the whirlpool effect. Baskets were not used in any case. All 5 mini-PCNLs had stone sizes 30-45 mm, with a mean of 37.5 mm.  Intraoperative complications were Gr1 mucosal ureteral injury in 2 patients and Gr 3 ureteral injury from access sheath in 1 patient which healed completely after stenting for 3 weeks. 138 patients have completed post-operative imaging (Low dose CT at 3 months). 114(82.6%) had achieved complete clearance (insignificant residual fragment i.e., < 4mm) at 3 months.

Conclusion

Despite various ex-vivo and few in-vivo studies using TFL, there is no clear consensus on ideal settings for dusting or fragmentation using TFL. This initial series using SP-TFL at a fixed setting has shown both efficient dusting as well as fragmentation at 0.5J and 70 Hz. Further studies comparing different laser settings and different stone composition needs to be done to find ideal settings for TFL.

Funding

None

Co-Authors

Puja Sengupta,
Lake Erie College of Osteopathic Medicine

Leann Shelmire, PA-C
St James Mercy Hospital