Comparison of cutting and coagulation properties of 1.56 and 1.94 µm fiber lasers and a 0.98 µm semiconductor laser

Aim of the study was to compare the cutting and coagulation properties of 1.56 and 1.94 μm fiber lasers with those of a 0.98 μm semiconductor laser.Materials and methods. A comparative study of the biological effects of 1.56 and 1.94 µm lasers and a 0.98 µm semiconductor laser used in a constant, continuous mode was carried out. The cutting properties of the lasers were evaluated on the chicken muscle tissue samples by the width and depth of the ablation zone formed via a linear laser incision at a speed of 2 mm/s, while the coagulation properties were assessed by the width of the lateral coagulation zone. The zones were measured using a surgical microscope and a calibration slide. For statistical analysis, power values of 3, 5, 7, 9, and 11 W were chosen for each laser wavelength.Results. Analysis of the findings confirmed that laser wavelength had a statistically significant effect on the linear dependence between incision parameters and laser power. It was found that the 1.56 μm fiber laser (water absorption) had a greater coagulation ability but a comparable cutting ability compared with the 0.98 μm laser (hemoglobin absorption). When used in the power mode of 7W or higher, the 1.94 µm laser provided superior cutting performance compared with the 0.98 µm semiconductor laser at the same exposure power. Elevating the power in any of the lasers primarily increased the width of the ablation zone, and to a lesser extent – the crater depth and the width of the lateral coagulation zone. Therefore, in comparison with the 0.98 μm semiconductor laser, higher radiation power in the 1.56 and 1.94 μm lasers mainly influences their cutting properties, expanding the width and depth of the ablation zone, and has a smaller effect on their coagulation ability.Conclusion. The findings of the study showed that the 1.56 and 1.94 μm fiber lasers have better coagulation properties in comparison with the 0.98 μm semiconductor laser. was statistically proven that all incision characteristics (width of the lateral coagulation zone, depth and width of the ablation zone) for the 1.56, 1.94, and 0.98 μm lasers depend on the power of laser radiation. The 1.94 µm laser is superior to the 0.98 µm laser in its cutting properties.

Failure of endoscopic management of ureteral strictures is due to ureteroscopic lithotripsy as a cause and longer length of stricture

Background Ureteroscopic lithotripsy is a common treatment for middle and lower ureteral stones. Although effective and minimally invasive, this technique might cause significant complications, including postoperative ureteral strictures, which occur in 1–4% of patients after ordinary ureteroscopic lithotripsy and in 7.8–24% when lithotripsy is performed for impacted stones. The main purpose of the management of ureteral strictures is to improve hydronephrosis and protect renal function. However, factors that influence the success rate of the endoscopic management of US (e.g., the cause and length of stricture, the duration of hydronephrosis, surgical management technique, and the number of placed ureteral stents) are controversial. The aim of this study was to investigate factors determining the outcomes of endoscopic management for stone-related ureteral stricture. Methods This multi-center case series study was performed at one of the highest-volume centers and the affiliated institutions in Japan. Data of patients who underwent endoscopic surgery for ureteral stricture from January 2016 to March 2019 were retrospectively analyzed. Laser incision and/or balloon dilation were performed for management; single or double stents were placed at the end of the surgery. Treatment success was defined as improvement in hydronephrosis status. Results Nineteen patients were treated for stone-related ureteral stricture. Hydronephrosis successfully improved in 12 patients (63.2%). All seven patients with failed endoscopic management had ureteroscopic lithotripsy-related stricture, whereas 3/12 (25.0%) and 7/12 (58.3%) patients with ureteroscopic lithotripsy-related stricture and impacted stone-related stricture, respectively, underwent successful endoscopic treatment (P = 0.004). Stricture length > 15 mm was observed in five patients (71.4%) with failed management, two patients (16.6%) with successful management (P = 0.046), 7/10 patients (70.0%) with ureteroscopic lithotripsy-related stricture, and 1/7 patients (14.3%) with impacted stone-related stricture (P = 0.049). Among patients with ureteroscopic lithotripsy-related stricture and impacted stone-related stricture, both laser incision and balloon dilation were performed in 5/10 (50.0%) and 2/7 (28.6%) patients (P = 0.874) while double stents were placed in 5/10 (50.0%) and 5/7 (57.1%) patients (P = 0.874), respectively. Conclusions Ureteroscopic lithotripsy as a cause and stricture length > 15 mm could strongly affect the success rate of endoscopic management of ureteral stricture. In such cases, reconstructive management should be considered in the early stages.