Outcomes of flexible ureterorenoscopy for solitary renal stones in the CROES URS global study

Purpose: we determined the efficacy and safety of flexible ureterorenoscopy for single intrarenal calculi and further stratified efficacy by stone burden.Materials and Methods: CROES collected prospective data on consecutive patients with urinary stones treated with ureterorenoscopy at 114 centers worldwide for 1 year. Only patients who underwent flexible ureterorenoscopy for a solitary renal stone were included in study. Preoperative and intraoperative characteristics, and postoperative outcomes were evaluated. Relationships between stone size and the stone-free rate, operative time, complications, hospital stay and need for re-treatment were determined.Results: a total of 1,210 patients with a solitary kidney stone less than 10 (52.2%), 10 to 20 (43.2%) and greater than 20 mm (4.6%) were treated with flexible ureterorenoscopy. The stone-free rate negatively correlated with stone size when adjusted for body mass index. Operative time positively correlated with stone size when adjusted for body mass index. The single session stone-free rate was 90% and 80% for stones less than 10 and less than 15 mm, respectively. Patients with stones greater than 20 mm achieved a 30% stone-free rate, more often needed re-treatment and were more often rehospitalized. There was no difference in the overall complication rate by stone size. However, patients with a stone greater than 20 mm showed a higher probability of fever after flexible ureterorenoscopy than those with a smaller stone.Conclusions: our data indicate that flexible ureterorenoscopy for a single intrarenal stone is a safe procedure. Best results after single session flexible ureterorenoscopy were obtained for stones less than 15 mm