Thulium fiber laser utilization in urological surgery: A narrative review

[Thulium or holmium laser or both: where will the journey take us?]

The Holmium:YAG laser has been the gold standard for laser lithotripsy over the past three decades and, since the late 1990s, also for prostate enucleation. Pulsed thulium fibre lasers (TFL) demonstrated their efficacy in in-vitro experiments and were introduced to the market a few years ago. Initial clinical results for TFL in lithotripsy and enucleation are very promising. In addition to TFL, a pulsed Thulium:YAG solid-state laser has been introduced, but clinical data for this laser are currently limited. This article aims to review the key technological differences between Ho:YAG lasers and pulsed thulium lasers and compare/discuss the initial clinical results for stone lithotripsy and laser enucleation.In-vitro studies have demonstrated the technical superiority of TFL compared with Ho:YAG lasers. However, as TFL is still a new technology, only limited studies are available to date, and optimal settings for lithotripsy have not been established. For enucleation, the differences of TFL compared with a high-power Ho:YAG laser seem to be clinically irrelevant. Initial studies on pulsed Tm:YAG lasers show good results, but there continues to be a lack of comparative studies.Based on the current literature, pulsed thulium lasers have the potential of being an alternative to Ho:YAG lasers. However, further studies are necessary to determine the optimal laser technology for enucleation and lithotripsy of urinary stones, considering all parameters, including efficacy, safety, and cost.

Flexible ureteroscopic treatment of kidney stones: How do the new laser systems change our concepts?

Objective

Flexible ureteroscopy (fURS) has become a widely accepted and effective technique for treating kidney stones. With the development of new laser systems, the fURS approach has evolved significantly. This literature review aims to examine the current state of knowledge on fURS treatment of kidney stones, with a particular focus on the impact of the latest laser technologies on clinical outcomes and patient safety.

Methods

We conducted a search of the PubMed/PMC, Web of Science Core Collection, Scopus, Embase (Ovid), and Cochrane Databases for all randomized controlled trial articles on laser lithotripsy in September 2023 without time restriction.

Results

We found a total of 22 relevant pieces of literature. Holmium laser has been used for intracavitary laser lithotripsy for nearly 30 years and has become the golden standard for the treatment of urinary stones. However, the existing holmium laser cannot completely powder the stone, and the retropulsion of the stone after the laser emission and the thermal damage to the tissue have caused many problems for clinicians. The introduction of thulium fiber laser and Moses technology brings highly efficient dusting lithotripsy effect through laser innovation, limiting pulse energy and broadening pulse frequency.

Conclusion

While the holmium:yttrium-aluminum-garnet laser remains the primary choice for endoscopic laser lithotripsy, recent technological advancements hint at a potential new gold standard. Parameter range, retropulsion effect, laser fiber adaptability, and overall system performance demand comprehensive attention. The ablation efficacy of high-pulse-frequency devices relies on precise targeting, which may pose practical challenges.

Acoustic emission of kidney stones: a medical adaptation of statistical breakdown mechanisms

Kidney stones have a prevalence rate of > 10% in some countries. There has been a significant increase in surgery to treat kidney stones over the last 10 years, and it is crucial that such techniques are as effective as possible, while limiting complications. A selection of kidney stones with different chemical and structural properties were subjected to compression. Under compression, they emit acoustic signals called crackling noise. The variability of the crackling noise was surprisingly great comparing weddellite, cystine and uric acid stones. Two types of signals were found in all stones. At high energies of the emitted sound waves, we found avalanche behaviour, while all stones also showed signals of local, uncorrelated collapse. These two types of events are called 'wild' for avalanches and 'mild' for uncorrelated events. The key observation is that the crossover from mild to wild collapse events differs greatly between different stones. Weddellite showed brittle collapse, extremely low crossover energies (< 5 aJ) and wild avalanches over 6 orders of magnitude. In cystine and uric acid stones, the collapse was more complicated with a dominance of local "mild" breakings, although they all contained some stress-induced collective avalanches. Cystine stones had high crossover energies, typically [Formula: see text] 750 aJ, and a narrow window over which they showed wild avalanches. Uric acid stones gave moderate values of crossover energies, [Formula: see text] 200 aJ, and wild avalanche behaviour for [Formula: see text] 3 orders of magnitude. Further research extended to all stone types, and measurement of stone responses to different lithotripsy strategies, will assist in optimisation of settings of the laser and other lithotripsy devices to insight fragmentation by targeting the 'wild' avalanche regime.

Thulium Laser for the Treatment of Posterior Urethral Valves in Infants

Objective: Thulium laser (ThL) has become popular in urology, because of its powerful action on tissue, achieving optimal ablation and hemostasis. Aim of our article was to evaluate efficacy of ThL in infants affected by posterior urethral valve (PUV) ablation. Patients and Methods: Clinical charts of 25 infants (age ≤12 months) who underwent PUV ablation were retrospectively reviewed. According to our protocol, all patients performed voiding cystourethrography and cystoscopy 6 to 8 months after initial treatment. Several factors, including age and weight at surgery, operative time, postoperative bleeding, catheterization period, postoperative urinary retention, retreatment for valve remnants, and stricture at follow-up, were evaluated. Preoperative, intraoperative, and postoperative data were analyzed. Results: Mean age at primary surgery was 4.5 months (5 days-10.5 months) and mean weight at primary surgery was 5.7 kg (2.5-10.3 kg). Mean operative time was 29.5 minutes (range 15-50 minutes). None of the patients experienced intraoperative and postoperative bleeding. In all cases, postoperative catheterization period was 1 day. Residual valves were found in 6 of 25 (24%) patients. No cases of urethral stricture were registered during follow-up (48.4 months, range: 11-95). Analyzing literature data using other techniques, complication rate of ThL PUV ablation seems lower than standard treatments (electrofulguration, cold knife) and comparable with those reported with other laser techniques. Conclusion: PUV ablation with ThL has proven to be feasible and safe in infants. Further studies are needed to define the real effectiveness of this laser technology in PUV ablation. Miniaturized instruments and ThL technology make early PUV treatment feasible also in low body weight newborns.

Occult renal artery pseudoaneurysm causing persistent hematuria after flexible Thulium fibered laser lithotripsy: A case report and literature review of rare but potentially fatal complication

Renal artery pseudoaneurysm may develop after laser flexible ureteroscopy stone lithotripsy (FURSL). Typical symptoms include flank pain, persistent hematuria, delayed refractory anemia, or hemorrhagic shock in case of pseudoaneurysm rupture. This complication of laser FURSL is very rare with only five cases reported in the literature as of April 2023, of which one involved Thulium laser. We report the case of a 65-year-old man with recurrent renal lithiasis who underwent FURSL using Thulium fibered laser (TFL) for 8 mm stone of left kidney upper pole. Persistent hematuria developed postoperatively, secondary to a pseudoaneurysm from a segmental branch of the left renal artery. It was diagnosed on arteriography performed for sudden hemorrhagic shock 27 days after surgery. Selective embolization with metallic micro-coils resolved hematuria. Although laser FURSL is often uncomplicated and TFL is regarded as safe, this complication should be suspected when refractory hematuria or hemodynamic instability follows the procedure. We report this case to add support to the current literature and outline procedural risk factors and useful precautions during the procedure.

Thulium Fiber Laser vs Pulse-Modulated Holmium MOSES Laser in Flexible Ureteroscopy for the Management of Kidney Stones: A Single-Center Retrospective Analysis

Introduction and Objective: The study's primary objective was to compare the laser efficiency and clinical outcomes of two widely used systems, the holmium MOSES laser and the thulium fiber laser (TFL), in managing kidney stones. The secondary outcomes were to evaluate the impact of stone composition on laser efficacy. Methods: We conducted a retrospective review of patients who underwent flexible ureteroscopy (f-URS) for solitary renal calculi between December 2020 and August 2022 at our institution and had a 3-month postoperative CT scan. Patient demographics and stone parameters were recorded, including stone site, size, volume, and density. Intraoperative data were collected and analyzed, including total operative time, ureteroscopy time, lasing time, technique, total energy delivered, and stone composition. All patients underwent a CT scan at 3 months follow-up. We recorded the presence of residual stones and the percentage of stone volume reduction. Ablation efficiency was calculated by dividing the energy utilized (J) by the stone volume (mm3). The ablation speed was calculated by dividing the stone volume (mm3) by the lasing time (seconds). Patients with a stone size <4 mm were deemed stone-free. Results: The MOSES and TFL groups comprised 62 and 49 patients, respectively. There were no significant differences between groups for baseline patient demographics or stone characteristics. The two modalities had comparable total energy, laser time, efficacy, and ablation speeds. No differences were detected in stone-free rates or complications between both groups. When dealing with calcium phosphate stones, we observed that the lasing time was significantly shorter with MOSES than TFL (7.95 vs 10.85 minutes, respectively [p = 0.01]). Conclusions: MOSES and TFL laser systems had comparable efficacy for lithotripsy of renal calculi during f-URS; however, calcium phosphate stones had a longer lasing time with TFL. REB Number: 100210.

Thulium fiber laser in endourology: current clinical evidence

PURPOSE OF REVIEW

To review and summarize preclinical and clinical data on thulium fiber laser's (TFL) effectiveness (ablation rate, stone-free rate etc.) and safety in terms of laser injuries and thermal damage. This enables us to assess how the in-vitro evidence translates into the clinical real-life scenario.

RECENT FINDINGS

In this analysis, a total of 21 preclinical trials have been included. Most of the trials use conventional Holmium:YAG laser as a comparator, with only a few assessing lasers with pulse modulation. Most of the trials focus on the superior ablation rate and superior dusting features of TFL, as well as comparison of retropulsion (both in conventional Ho:YAG and in a pulse modulation), with a few studies assessing safety aspects. A total of 13 trials assessed TFL, clinically, in percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS). The clinical data obtained suggest that lithotripsy by TFL is safe, facilitates effective stone fragmentation, and results in a reduction of retropulsion. Unfortunately, most of the clinical trials lack a direct comparator, and so no clear-cut comparisons are possible.

SUMMARY

During in-vitro studies, TFL demonstrated to be a new energy source with a great potential for improved ablation, lower retropulsion and improved dusting. These claims are supported in contemporary clinical studies, reporting superior ablation and negligible retropulsion in both PCNL and RIRS. However, it should be noted that the data regarding clinical results compared with conventional Ho:YAG is still limited.

Lithotripsy devices for percutaneous nephrolithotomy (PNL) - new developments

PURPOSE OF REVIEW

Percutaneous nephrolithotomy (PNL) is the mainstay of surgery for renal calculi>2 cm or complex multiple calculi and is a technique that has been around since 1976. We review recent literature surrounding novel lithotripsy devices and technology used in PNL.

RECENT FINDINGS

At present, the Holmium:yttrium-aluminum-garnet (Ho:YAG) laser is widely accepted as the gold standard laser lithotripsy for PNL. SwissLithoClast Trilogy offers a range of probes with a trifecta of electromagnetic, ultrasonic energy with surgeon-controlled suction. The Olympus Shockpulse-SE is a similar lithotripter that relies on continuous ultrasonic energy with pulsed ballistic energy to break stones. Thulium Fiber Laser (TFL) offers an alternative laser energy source to the Holmium laser, which has been shown to be very effective at producing small stone fragments and dust. The Moses technology is another addition in a long list of improvements to the Ho:YAG laser, forming vaporization bubble through which more effective energy can be applied to stones.

SUMMARY

Trilogy, Shockpulse, TFL and Moses pulse modulation technology for the Holmium laser all provide improvements compared with older lithotripsy devices. In particular, they convey a safer, efficient and more effective way to manage and clear stones.

New Lasers for Stone Treatment

Laser technology has been a breakthrough in urology. The new era in endocorporeal laser lithotripsy has recently begun in mid-2020, where promising technologies tested in vitro have reached their approval for clinical use and, in that way, have made it possible to confirm their safety and advantages in the real world, for the patient and for the urologist.