Residual Fragments Following Ureteroscopic Lithotripsy: Incidence and Predictors on Postoperative Computerized Tomography

PURPOSE: Residual fragments following ureteroscopy for calculi may contribute to stone growth, symptoms or additional interventions. We reviewed our experience with ureteroscopy for calculus disease to define the incidence and establish factors predictive of residual fragments. MATERIALS AND METHODS: Records associated with 667 consecutive ureteroscopic lithotripsy procedures for upper urinary calculi were reviewed. In 265 procedures (40%) computerized tomography was done between 30 and 90 days postoperatively. They comprised the study group. Residual fragments were defined as any residual ipsilateral stone greater than 2 mm. RESULTS: Included in the study were 121 men and 127 women with a mean age of 47 years. Mean target stone diameter was 7.6 mm. The stone location was the kidney in 30% of cases, ureter in 50%, and kidney and ureter in 20%. Residual fragments were detected on computerized tomography after 101 of 265 procedures (38%). Pretreatment stone size was associated with residual fragments at a rate of 24%, 40% and 58% for stones 5 or less, 6 to 10 and greater than 10 mm, respectively (p <0.001). Additionally, stone location in the kidney (p <0.001) or the kidney and ureter (p = 0.044), multiple calculi (p = 0.003), longer operative time (p = 0.008) and exclusive use of flexible ureteroscopy (p = 0.029) were associated with residual fragments. In a multivariate model only pretreatment stone diameter greater than 5 mm was independently associated with residual fragments after ureteroscopy (diameter 6 to 10 and greater than 10 mm OR 2.03, p = 0.03 and OR 3.74, p = 0.003, respectively). CONCLUSIONS: Of patients who underwent ureteroscopic lithotripsy for calculi 38% had residual fragments by computerized tomography criteria, including more than 50% with stones 1 cm or greater. Such data may guide expectations regarding the success of ureteroscopy in attaining stone-free status.