Ho:YAG Laser Versus Thulium Laser for the Management of 2-4cm Kidney Stones During SMP（Suction Mini Percutaneous Nephrolithotomy）：An International Multicenter Randomized Controlled Trial

With the rapid development of medical equipment and the increasing experience, minimally invasive percutaneous nephrolithotomy (mini-PCNL) has been a well established modality for the management of upper urinary tract stones. The introduction of negative pressure suction technology into mini-PCNL can actively suck out the perfusion fluid and stone fragments, therefore to speed up stone removal efficency and keep a low intrarenal pressure, and was called suction mini-PCNL (SMP).

The common energy sources for SMP were pneumatic ballistic lithotripsy and Ho:YAG laser. The handle of pneumatic ballistic lithotripsy was heavy and can not be fixed on the nephroscope, furthermore, the fragments in pneumatic ballistic lithotripsy was large, therefore the active suction and discharge of stone fragments can not be well completed at the same time of lithotripsy. However, the Ho:YAG laser can well match the requirement of SMP that lithotripsy and suction can work at the same time. Recently, thulium fiber laser (TFL) was also used for lithotripsy. The versatility of TFL, including high frequencies and reduced retropulsion may result in higher ablation efficiency compared to Ho:YAG laser. However, there is no clinical study on the difference between Ho:YAG laser and thulium laser in SMP, which limits the reasonable choice of laser in SMP to a certain extent.

So, the investigators would like to have an international multi-centre RCT to compare the therapeutic effects of SMP with Ho:YAG laser versus TFL in the treatment of 2-4cm renal calculi, so as to provide high-level evidence to support for clinical selection.