Role of Residual Fragments on the Risk of Repeat Surgery after Flexible Ureteroscopy and Laser Lithotripsy: Single Center Study.

PURPOSE: We analyzed the impact of residual stone fragments seen on abdominal x-ray after ureteroscopy and laser lithotripsy on the risk of repeat surgical intervention. MATERIALS AND METHODS: Our study included 781 patients (802 renal units) who underwent ureteroscopy and laser lithotripsy with abdominal x-ray within 3 months postoperatively and who had at least 1 year of followup. Ureteroscopy and laser lithotripsy were performed using the dusting technique. We analyzed the association between surgical recurrence-free survival and the size of the largest residual fragment. RESULTS: During a median followup of 4.2 years repeat surgery was performed on 161 renal units (20%). Of the repeat interventions 75% were done for symptomatic nephrolithiasis. Postoperative imaging showed residual stone fragments in 42% of cases. In the entire group the risk of repeat surgery was increased in renal units with residual fragments greater than 2 mm. The effect of the size of residual fragments on the risk of surgical recurrence varied by patient body mass index. It was much larger in nonobese subjects, who were at increased risk for repeat surgery with residual fragments of any size. In the obese subgroup only fragments greater than 2 mm increased the risk of surgical recurrence. CONCLUSIONS: The association between the size of residual stone fragments detected by abdominal x-ray after ureteroscopy and laser lithotripsy, and the risk of repeat surgical intervention depends on patient body mass index. Nonobese patients with residual stone fragments of any size are at increased risk for repeat intervention compared to those with a negative abdominal x-ray. The predictive value of abdominal x-ray after ureteroscopy and laser lithotripsy is limited in obese patients.