Comparison of low power and high power holmium YAG laser settings in flexible ureteroscopy.

PURPOSE: To compare the efficacy of conventional low power and high power holmium: yttrium aluminum-garnet (Ho: YAG) laser lithotripsy settings during retrograde intrarenal surgery (RIRS).  METHODS: The prospective study was conducted in patients undergoing RIRS for renal stones less than 2 cm diameter. Pulsed Ho:YAG laser (Lumenis® Pulse TM P120 H) was used for laser lithotripsy and the patients were randomized into low power (LP) and high power (HP) laser lithotripsy settings groups. The lasing duration, total laser energy used (Joules), laser energy used to ablate 1 mm3 of stone (Joules/mm3), operative duration, stone ablation speed (mm3/s) and stone free rate were compared. RESULTS: A total of 120 underwent RIRS with 63 and 57 patients in LP and HP group, respectively. Median stone volume and stone density were comparable between the groups. The total energy used and laser energy used to ablate 1mm3 of stone (Joules/mm3) were significantly higher in the HP group than in LP group (27.9 (16.4-46.2) J/ mm3 vs 9.7 (5.3-17.7) J/ mm3) (p < 0.01). Median (IQR) ablation speed were 0.8 (0.5-1.3) mm3/s and 0.6 (0.4-1) mm3/s in the LP and HP groups, respectively. The median lasing time, operative time and stone free rate were similar in both the groups. CONCLUSION: The total energy used and J/mm3 were lower in the LP group than in HP group with similar lasing duration, operative duration, ablation speed and stone free rate for renal stones less than 2 cm.