In a study examining endoscopic treatments for urinary stones in pediatric patients, researchers at Boston Children’s Hospital found that use of thulium fiber lasers may improve patient outcomes. The researchers compared results of laser lithotripsy performed using two types of laser systems: a low-power holmium:yttrium-aluminum-garnet (Ho:YAG) laser and a super-pulsed thulium fiber (SPTF) laser. Laser lithotripsy, an endoscopic procedure for treating stones in the ureter, delivers laser energy to the urinary system through an optical fiber. The laser breaks the stones into pieces small enough to be passed in the urine. Currently, the Ho:YAG laser is considered the gold standard for endoscopic treatment of pediatric urolithiasis due to its clinical efficacy, safety, and durability. However, the 2120-nm beam from a Ho:YAG laser leads to less stone ablation than the 1940-nm beam from a thulium fiber laser. A thulium fiber laser beam can be delivered in continuous or pulsed mode and in a range of energy and frequency settings. Although Ho:YAG lasers can operate in different pulsed modes, their energy and frequency ranges are narrow compared to thulium fiber lasers, which use an energy-efficient laser diode system to produce a laser beam. In a thulium fiber laser, heat is dissipated with a fan, which makes less noise and takes up less space than the complex refrigeration system used in Ho:YAG lasers. A Ho:YAG laser requires a flash-lamp for low-power beams and a series of flash-lamps for high-power beams. The researchers evaluated the clinical performance of low-power Ho:YAG lasers and SPTF lasers in a retrospective study of pediatric patients who received treatment from 2016 to 2021. A total of 125 procedures were performed on 109 patients; 93 patients were treated using a low-power Ho:YAG laser, and 32 were treated using a SPTF laser. Based on analyses controlling for patient age and stone burden, the odds of having a residual fragment after treatment were shown to be about 60% lower with the use of the SPTF laser — a significant finding since residual stone fragments of any size can require further treatment. On their first imaging scan after treatment, 62% of patients were free of any residual stone fragments. The stone-free rate was 59% in Ho:YAG cases compared to 70% in SPTF cases. Use of the SPTF laser resulted in a cumulative 11% improvement in stone-free rate. Operative times and complication rates for the two groups were similar, though laser time was longer in the SPTF group. Based on their experience as early adopters of the SPTF laser technology for the treatment of pediatric urinary stones, Christopher Jaeger and his colleagues at Boston Children’s Hospital believe that the SPTF laser could improve operative outcomes for young patients undergoing ureteroscopy. “The SPTF laser using thulium fiber laser technology is an effective alternative to the low-power Ho:YAG laser for treatment of urolithiasis in pediatric patients,” the team members said. Further studies are needed to determine optimal SPTF settings and compare STPF to high-power Ho:YAG lasers. The team also noted that previous studies have shown the advantages of the SPTF laser system for treatment of urinary stones in adults. The research was published in The Journal of Urology (www.doi.org/10.1097/JU.0000000000002666).