Laser lithotripsy is widely used for the treatment of ureteral and renal stones. However, intrarenal temperature elevation during laser activation has become a topic of concern due to potential thermal injury. Sustained exposure to elevated temperatures can impair renal function, induce urothelial damage, and lead to long-term complications such as strictures, adversely affecting patient outcomes and increasing treatment costs. This study aims to evaluate the relationship between laser power, irrigation rates, and intrarenal temperature changes in an ex vivo kidney model.

A prospective experimental study was conducted using an anatomically accurate 3D-printed kidney model, with and without the presence of renal stones. Laser lithotripsy was performed using two power settings (25W and 40W) under varying irrigation conditions: no irrigation, 15 ml/min, and 40 ml/min. Key parameters measured included intrarenal temperature dynamics, mean and peak temperatures, time to reach threshold values (43°C and 56°C), total laser activation time, and energy delivered. Temperature thresholds of 43°C (threshold for tissue damage) and 56°C (protein denaturation) were used as safety markers.

In the absence of irrigation, critical temperatures were reached rapidly: at 25W, 43°C was reached after 9 sec and 56°C after 64 sec; at 40W, these values were 3 sec and 16 sec, respectively. With irrigation at 15 ml/min and no stone, 25W reached 43°C in 10 sec (56°C not reached), while 40W reached 43°C in 6 sec and 56°C in 43 sec. At 40 ml/min irrigation, 25W did not reach critical temperatures, and 40W reached 43°C only after 112 sec. When stones were present, similar trends were observed: without irrigation, 25W reached 43°C in 6 sec and 56°C in 91 sec; 40W in 7 sec and 51 sec, respectively. With 15 ml/min irrigation, 25W reached 43°C in 76 sec (56°C not reached), while 40W reached 43°C in 11 sec and 56°C in 110 sec. At 40 ml/min, neither laser power reached critical temperature thresholds.

This study demonstrates that irrigation flow rate significantly influences temperature control during laser lithotripsy. An irrigation rate of 15 ml/min appears acceptable for short laser activation times at 25W, but caution is warranted due to the proximity to thermal thresholds. The most thermally safe condition was achieved at 40 ml/min, where critical temperatures were not reached, even at high power. However, elevated irrigation rates may increase intrarenal pressure, necessitating further studies to assess safety in vivo.