(UroToday.com) A novel study presented by Mr. Yutaro Tanaka of Nagoya City University, Japan, investigated the potential of using femtosecond lasers for urinary stone surgery. The study, aiming to address complications associated with traditional Holmium YAG lasers, showcased promising results in achieving precise stone ablation while minimizing thermal damage and shock waves.
Traditionally, Holmium YAG lasers have been widely used in urological surgery, particularly for endoscopic lithotripsy. However, their utilization has often led to severe complications such as ureteral stricture and injury due to the significant thermal effects generated during treatment. Moreover, the scattering of stone fragments by powerful shock waves complicates surgical procedures as the field of view is often obstructed.
In contrast, femtosecond lasers, known for their precision in various laser processing applications, offer a potential solution. The study involved the collection of urinary stones of different compositions from patients, which were then subjected to irradiation with both femtosecond lasers and Holmium YAG lasers in ex vivo experiments conducted in both air and water environments.
Results from the study revealed a stark difference between the two laser types. Lateral repulsion of stones using both Holmium YAG and femtosecond lasers. The Holmium YAG caused the stone to repulse 10 cm back, while Femtosecond lasers caused no repulsion. Water temperature was increased by 30°C using Holmium, compared to only 5°C using femtosecond lasers. Mr. Tanaka went on to describe the thermal damage observed on tissue when using each laser, respectively. Thermal damage was observed from the submucosal layer to the muscular layers. Furthermore, femtosecond lasers only showed damage to superficial layers of tissue.
Femtosecond lasers demonstrated precise cutting of urinary stones with minimal retropulsion, regardless of stone composition or environmental conditions. In contrast, Holmium YAG lasers fragmented stones with strong shock waves and rapid temperature increases, leading to thermal alteration of the stone surfaces. 
Detailed examination of the stone cross-sections further highlighted the advantages of femtosecond lasers, showcasing smooth surfaces with micrometer-scale precision. These findings suggest the potential for femtosecond lasers to revolutionize urinary stone surgery by offering a technique that can safely cut tissues while minimizing thermal damage and shock waves.
The implications of this study are significant, signaling a potential shift in urological surgical practices toward the adoption of femtosecond lasers. If further validated through clinical trials and real-world applications, this technology could offer safer and more effective treatment options for patients with urinary stones, potentially reducing the risk of complications and improving surgical outcomes.
After the presentation, a urologist from Duke University inquired about the precise mechanism that femtosecond lasers use to carry out thermal ablations. Mr. Tanaka responded, “They cut the molecular bond of the tissue by photo-disruption, so it does not cause heat generation”.
One of the moderators, Dr. Naeem Bhojani, asked how long it would take to complete a cut. Mr. Tanaka responded, “It takes a long time because it is still very low energy…about 30 minutes to 1 hour”. Dr. Bhojani humorously responded, “urologists are not that patient”. Certainly, the femtosecond laser has the potential to be used clinically, but ablation times will limit its ability to be implemented into clinical practice in the near future.
Overall, the study represents a significant step forward in the field of urology, highlighting the transformative potential of femtosecond lasers in advancing surgical techniques and improving patient care.
Presented by: Yutaro Tanaka, Department of Nephro-Urology, Nagoya City University, JapanWritten by: Mark Sarwat Hana, Assistant Research Specialist, Department of Urology, University of California Irvine, during the 2024 American Urological Association (AUA) Annual Meeting, May 2 - 6, 2022, San Antonio, Texas