Predictive factors of stone-free status in renal stone treatment with flexible ureterorenoscopy

Abstract

Objective: Flexible ureterorenoscopy (fURS) is one of the standard treatments for renal calculi up to 20 mm. This study aims to identify factors associated with stone-free status. Materials and Methods: We included patients undergoing fURS for treatment of small to medium-size renal stone (no single stone larger than 20 mm) from April 2017 to September 2019 at King Chulalongkorn Memorial Hospital. All patients had a preoperative CT scan and postoperative imaging for comparison. We collected patient characteristics (sex, age, previous ipsilateral urinary tract surgery, preoperative ureteral stent placement), stone factors (total stone burden, stone number, stone density) and renal factors (anatomical abnormalities, stone location in a lower pole, number of caliceal involvement) and correlated the data against postoperative stone-free status (defined as residual fragment ≤ 2 mm). Results: The overall stone-free rate was 53.3%. From the univariate analysis, previous surgery, total stone burden, stone number, stone location in the lower pole, and the number of caliceal involvement were associated with stone-free status. However, only the total stone burden remained statistically significant in the multivariate analysis (p-value < 0.05). The stone-free rates were 75.9%, 57.1%, and 11.1% in the total stone burden ≤ 10 mm, 11-20 mm, > 20 mm, respectively. Conclusion: Following treatment of renal stones ≤ 20 mm with fURS, the stone-free rate was 53.3% and was significantly associated with the preoperative total stone burden.