Computed tomography-determined stone-free rates for ureteroscopy of upper-tract stones

Background and Purpose: Most series on ureteroscopy for urolithiasis use postoperative plain radiography of the kidneys, ureters, and bladder (KUB) or intravenous urography (IVU) to determine outcomes. These imaging modalities, however, are not very sensitive and may overestimate stone-free rates (SFRs). The aim of our study was to assess SFRs after ureteroscopy for urolithiasis using CT follow-up. Patients and Methods: A total of 92 patients underwent 113 ureteroscopic procedures for either renal or ureteral stones. Success of ureteroscopy was then determined by the absence of any stone fragments (stone-free). Stone-clearance rates (SCRs) were also calculated for ≤2mm and ≤4mm residual stone fragments. Results: Each renal unit contained a mean of 1.87stones with a mean stone diameter of 8± 6mm. The overall SFR was 50.4%. SFRs were significantly higher for ureteral stones (80%) than renal stones (34.8%) (P= 0.0001). Renal units with multiple stones were less likely to be stone free than those with single stones (P= 0.011). No difference in SFRs was found between lower pole and non-lower-pole stones. Conclusions: Overall SFRs by CT were lower than SFRs reported by radiography of the KUB or IVU criteria. Further studies to identify the clinical significance and natural history of residual stone fragments on CT scan after ureteroscopy are needed.