Factors affecting the intraoperative calculi excretion during flexible ureteroscopy lithotripsy: an in vitro analysis

To explore the parameters influencing intraoperative calculi excretion (ICE) during flexible ureteroscopy lithotripsy (fURL) using in vitro simulation experiments.

3D-printed human kidney models were used to simulate the elimination of gravel during fURL. The factors influencing the ICE during fURL were analyzed by comparing the effects of different degrees of hydronephrosis (mild, moderate, and severe), surgical positions (supine and lateral position), ratios of endoscope-sheath diameter (RESD) (0.625, 0.725, and 0.825), gravel sizes (0.50–1.00 mm, 0.25–0.50 mm, and 0.10–0.25 mm), and ureteral access sheaths (UASs) (traditional UAS and negative-pressure UAS) on ICE.

The impacts of various UAS, RESD, degree of hydronephrosis, surgical positions, and gravel sizes on ICE were all significant (p < 0.05). We found no evidence of multicollinearity for all the independent variables, and the linear regression equation fitted as \(\mathrm{ICE }\,({\mathrm{g}}/{\mathrm{min}}) = 0.102 + 0.083*\mathrm{UAS\,grade }- 0.050*\mathrm{RESD\,grade }- 0.048*\mathrm{hydronephrosis\,grade }+ 0.065*\mathrm{position\,grade }- 0.027*\mathrm{gravel\,size\,grade}\) $\mathrm{ICE}(\mathrm{g}/\min )=0.102+0.083\ast \mathrm{UAS}\mathrm{grade}-0.050\ast \mathrm{RESD}\mathrm{grade}-0.048\ast \mathrm{hydronephrosis}\mathrm{grade}+0.065\ast \mathrm{position}\mathrm{grade}-0.027\ast \mathrm{gravel}\mathrm{size}\mathrm{grade}$ (R² = 0.569).

Employing negative-pressure UAS, smaller RESD, milder hydronephrosis, lateral position, and smaller gravel size contribute to improved ICE during fURL. Among them, the adoption of negative-pressure UAS had the most substantial effects.