Holmium laser percutaneous nephrolithotripsy was simulated by porcine kidney calculus model in vitro to investigate thermal damage of renal tissue by different energy parameters of the holmium laser.

We placed human kidney calculus specimen in fresh vitro porcine kidney, then insert thermocouple temperature probes into the submucosa of the renal pelvis and reheated in a 37 °C water bath. A percutaneous nephrological sheath was used to penetrate the renal parenchyma with a moderate irrigation rate of 30 ml/min at 18 ℃. The Holmium laser was used to fragment the stones under a nephroscope, and the temperature was recorded.

The four independent models were lithotripsy with 30 W and 60 W laser for 5 and 10 min, respectively; the mean temperature of 30 W vs. 60 W within 5 min was 36.06 °C vs. 39.21 °C (t = 5.36, P < 0.01) and the highest temperature was 43.60 °C vs. 46.60 °C; the mean temperature of 30 W vs. 60 W within 10 min was 37.91 °C vs. 40.13 ℃ (t = 5.28, P < 0.01), maximum temperature 46.80 ℃ vs. 49.20 ℃. Pathologically, each kidney was observed to have different degrees of thermal damage lesions, and the higher power and longer time the more severe the injury, but the injury was mainly limited to the uroepithelial and subepithelial tissues, with rare damage to renal tubules.

The higher laser excitation power and longer duration raised the intrarenal temperature significantly and caused a certain degree of thermal damage to the kidney tissue, but overall it was found to be safe and reliable. Urologists can avoid further side effects through surgical expertise.