Thulium:YAGVersusHolmium:YAG Laser Effect on Upper Urinary Tract Soft Tissue: Evidence from anEx VivoExperimental Study

Introduction:There are limited data regarding the effect of thulium laser (Tm:YAG) and holmium laser (Ho:YAG) on upper urinary tract. The aim of this study was to compare soft tissue effects of these two lasers at various settings, with a focus on incision depth (ID) and coagulation area (CA). Materials and Methods:Anex vivoexperimental study was performed in a porcine model. The kidneys were dissected to expose the upper urinary tract and the block samples containing urothelium and renal parenchyma were prepared. The laser fiber, fixed on a robotic arm, perpendicular to the target tissue was used with a 100 W Ho:YAG and a 200 W Tm:YAG. Incisions were made with the laser tip in contact with the urothelium and in continuous movement at a constant speed of 2 mm/s over a length of 1.5 cm. Total energy varied from 5 to 30 W. Incision shape was classified as follows: saccular, triangular, tubular, and irregular. ID, vaporization area (VA), CA, and total laser area (TLA = VA + CA) were evaluated. Statistical analysis was performed using the SPSS V23 package,p-values Results:A total of 216 experiments were performed. Incision shapes were saccular (46%), triangular (38%), and irregular (16%) with the Ho:YAG, while they were tubular (89%) and irregular (11%) with the Tm:YAG. ID was significantly deeper with the Ho:YAG (p = 0.024), while CA and TLA were larger with the Tm:YAG (p < 0.001 andp < 0.005). Conclusion:ID was deeper with Ho:YAG, whereas CA and TLA were larger with the Tm:YAG. Considering surgical principles for endoscopic ablation of upper tract urothelial carcinoma, these results suggest that Tm:YAG may have a lower risk profile (less depth of incision) while also being more efficient at tissue destruction. Futurein vivostudies are necessary to corroborate these findings.

Automated summary

This study compared the effects of Holmium laser (Ho:YAG) and Thulium laser (Tm:YAG) on upper urinary tract soft tissues in an ex vivo experimental study. The results showed that Ho:YAG produced deeper incisions, while Tm:YAG led to larger coagulation areas and total laser areas. Future in vivo studies are needed to confirm these findings.