What is the stone-free rate following flexible ureteroscopy for kidney stones?

Flexible ureteroscopy (URS) is increasingly being used as the first-line treatment for patients with renal stones. Despite this increase in use, substantial variations exist in the reported stone-free rates (SFR) following flexible URS. These variations are a result of inconsistencies in the definition of 'stone-free', which reflect variations in the type of imaging used to assess the presence of stones postoperatively and the timing of the assessment. Other possible factors such as the importance of residual fragments following stone surgery, and the size and position of the stones might also account for variations in stone-free rates. In order to obtain an accurate estimate of the SFR, especially within subgroups defined by stone characteristics and exact technique, we compare reported SFRs from studies that use imaging other than CT for follow-up and those that use only CT. We also review the evidence on the importance of active retrieval of fragments during flexible URS and whether this technique improves the outcomes of patients with kidney stones.