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Thesis Format



Master of Science




Razvi, Hassan

2nd Supervisor

Bjazevic, Jennifer



The Holmium:yttrium-aluminium-garnet (Ho:YAG) laser has become an indispensable tool in Endourology since its introduction in 1995, due to its safe and efficient urinary stone fragmentation capabilities. The Thulium Fiber Laser (TFL), is the latest innovation with early clinical experience suggesting improvements over the Ho:YAG. This prospective, randomized controlled study aims to compare clinical outcomes of Ho:YAG versus TFL lithotripsy for upper urinary tract calculi. Patients undergoing ureteroscopy for renal stones (size 8-20mm, density >600 HU) from a single institution were prospectively recruited.

Thirty-eight patients have been recruited (Ho:YAG=20, TFL=18). The laser-on time (p=.330), total operative time (p=.849), total laser energy (p=.745), ablation speed (p=.745) and ablation efficiency (p=.745) were not statistically different between groups. Multiple trends in favor the TFL were documented, including shorter laser-on time and total operative time, improved ablation efficiency and ablation speed.

Preliminary results suggest similar outcomes for both technologies. Several parameters are trending in favor of the TFL being more efficient; however, recruitment fulfillment will be necessary to determine if there are significant differences.

Summary for Lay Audience

Kidney stone disease is a common disease and has an estimated lifetime prevalence of 1-15%. Lithotripsy is a generic term used to describe procedures to destroy a stone inside the urinary tract, and can involve various technologies. Laser lithotripsy became the mainstay treatment since 1995, using the Holmium:yttrium-aluminium-garnet (Ho:YAG) wavelength. The laser delivers energy directly to the stone via an endoscope that allows direct vision and precise stone destruction. The Ho:YAG is widely used because of its safety and efficiency in destroying stones but has some inherent limitations. In 2005, a new laser technology was introduced, the Thulium Fiber Laser (TFL). The TFL has different physical properties, and laboratory and early clinical evidence demonstrated that it results in faster and more efficient laser destruction of urinary stones. The existing international literature is still scarce however, with few properly conducted high-quality clinical trials and controversy regarding the TFL’s advantages exists.

The aim of this research was to compare the Ho:YAG and TFL laser technologies in a clinical setting. A prospective recruitment of patients was undertaken, and patients were randomly assigned to each technology. To compare the efficiency of the lasers, different parameters were analyzed including: lasering time, surgical time, energy needed to destroy a stone and the speed at which the stone was destroyed. The preliminary findings of the research documented no statistical difference, but multiple parameters favored the TFL, as being a faster and more efficient laser. Nevertheless, recruitment fulfillment is needed to confirm any clinical differences. The clinical relevance of a more efficient laser lithotripsy laser is the ability to manage more complex and larger stones via a minimally invasive surgical approach which would improve patient care.

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