A simulated model for fluid and tissue heating during pediatric laser lithotripsy

Area of Science:

• Pediatric Urology
• Biomedical Engineering
• Nephrolithiasis Treatment

Background:

• Laser lithotripsy (LL) is a common treatment for kidney stones in children and adolescents.
• Higher-powered lasers may improve stone dusting but raise concerns about tissue damage due to fluid heating.
• The impact of pediatric urinary tract development on LL-induced thermal effects is not well understood.

Purpose of the Study:

• To investigate how fluid and tissue heating during laser lithotripsy (LL) varies with pediatric urinary tract development.
• To hypothesize that younger children's kidneys are more susceptible to thermal damage from LL.
• To evaluate the influence of irrigation flow rates and laser power settings on thermal dose in pediatric patients.

Main Methods:

• Computational simulations using COMSOL Multiphysics finite-element modeling were developed for LL in children aged 3, 8, and 12 years.
• Simulations incorporated varying irrigation flow rates (gravity vs. pressure), treatment locations, and laser power settings (5-40W).
• Thermal dose and tissue volume at risk for irreversible damage were calculated based on heat transfer, tissue properties, and blood flow.

Main Results:

• Laser lithotripsy at 20W and 40W with gravity flow irrigation generated thermal doses sufficient for tissue injury in all simulated pediatric ages.
• Younger children exhibited higher temperature increases across all power settings.
• Continuous pressure flow irrigation and intermittent laser activity significantly reduced temperature elevations.

Conclusions:

• Smaller renal size increases susceptibility to thermal changes during LL.
• Laser power settings of 20W or higher can cause thermal damage regardless of patient age.
• Continuous pressure flow irrigation and intermittent laser use are recommended to mitigate thermal risks in pediatric LL.