Stone size is a predictor for residual stone and multiple procedures of endoscopic combined intrarenal surgery

The aim of this study was to identify the predictors of treatment results after endoscopic combined intrarenal surgery (ECIRS).

A retrospective analysis was conducted of 75 patients with renal stones who underwent ECIRS and a preoperative non-contrast computed tomography (NCCT) examination. The stone-free rate (SFR), number of primary procedures and perioperative complications were investigated, and the predictors contributing to these three outcomes were analyzed. Stone-free status was determined within 3 months postoperatively using NCCT. The number of primary procedures (defined as ECIRS and/or conventional transurethral lithotripsy) and perioperative complications were reviewed using the medical records.

The final SFR after further treatment was 69.3% (52/75 cases). About 70% of all cases underwent only one primary procedure, and the average number of primary procedures was 1.41. From multivariate analysis, increasing stone size (p < 0.001), increasing Charlson Comorbidity Index (p = 0.043) and unfavorable nephrostomy tract (p = 0.046) were independent significant predictors of residual stones, and increasing stone size was the only independent significant predictor of two or more primary procedures (p = 0.017). Overall, 24 out of 75 patients (32%) experienced one or more perioperative complications. Based on multivariate analysis, female gender (p = 0.014) and increasing Hounsfield units (p = 0.006) were significantly associated with perioperative complications.

Increasing stone size was an independent predictor for residual stone and multiple procedures of ECIRS. In contrast, increasing number of involved calyces was not predictive, which may be responsible for the combined antegrade and retrograde access. Female gender and increasing Hounsfield units of the stone were significantly associated with perioperative complications of ECIRS, and ECIRS for these patients requires careful attention.