Stone-Event-Free Survival After Ureteroscopic Lithotripsy According to Residual Fragment Size: Zero Residual Fragment Indicates a Good Prognosis.

OBJECTIVES

This study aimed to evaluate how residual renal stone fragment size influences long-term stone-event-free survival after ureteroscopic lithotripsy (URSL), highlighting its clinical importance.

METHODS

We retrospectively analyzed data from all patients who underwent URSL at our institution from 2008 to 2021. A total of 1334 cases were included and categorized into three groups based on their residual renal fragment size: 0 mm (1030 cases), < 4 mm (214 cases), and ≥ 4 mm (90 cases). Patient characteristics, surgical outcomes, and postoperative stone events were examined. Stone event-free survival rates were compared across these groups.

RESULTS

During a mean follow-up of 763 days, 214 patients (16.0%) experienced stone events. The number of stone events in each group was 102 (9.9%) for 0 mm, 57 (26.6%) for < 4 mm, and 55 (61.1%) for ≥ 4 mm. The 1-year stone-event-free rates were 95.8%, 86.9%, and 44.9%, respectively, and the 5-year rates were 81.8%, 51.6%, and 28.0%. The reintervention-free rates at 1 year were 97.4%, 91.7%, and 50.5%, respectively, and at 5 years, they were 86.3%, 61.6%, and 35.5%. The log-rank test indicated significant differences in both stone-event-free and reintervention-free rates among the groups (p < 0.001). The multivariate Cox regression analysis revealed that the size of residual stones (0 mm versus < 4 mm and ≥ 4 mm) was the most significant factor in influencing stone events and re-interventions.

CONCLUSIONS

The size of residual fragments after URSL significantly influences long-term outcomes, emphasizing the importance of meticulous stone removal for optimal patient care.