Rethinking thermal safety in laser lithotripsy: a systematic review of thermal dose thresholds

To perform a systematic review of cumulative equivalent minutes at 43 °C (CEM43) threshold considered by endourology literature to induce tissue thermal damage.

While empirical strategies to reduce temperature have been suggested, the concept of thermal dose provides a more accurate framework to assess thermal injury, as it integrates both temperature and exposure duration.

A systematic review was performed in accordance with PRISMA checklist regarding thermal dose and laser lithotripsy. Eight hundred and fifty-seven articles were identified, and 19 were considered for final analysis. All of them based the thermal dose calculation on the model by Sapareto and Dewey. The most common threshold used was CEM43 at least 120 min. However, this value has not been empirically validated for renal tissue and may significantly overestimate its thermal tolerance. Evidence suggests that renal thermal damage can occur at CEM43 values as low as 20-70 min. The thermal dose concept allows to understand the profile of temperature that might be safe. The classical thresholds proposed in endourology papers seems to be well above the actual tolerance of renal tissue. Caution should be taken with laser settings to avoid potential cell injury due to overheating during laser lithotripsy.