Predictors of Clinical Significance of Residual Fragments after Extracorporeal Shockwave Lithotripsy for Renal Stones

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Abstract
To determine the predictors of the clinical outcome of residual fragments after extracorporeal shockwave lithotripsy (SWL). During the last 10 years, residual fragments < or =5 mm were present in 99 male and 55 female patients (mean age 43.1 years) for >3 months after SWL for renal stones. Follow-up with history, urine examination, and non-contrast CT scanning was carried out every 6 months or when symptoms developed. Clinically insignificant residual fragments were diagnosed in patients who became stone free or had asymptomatic fragments of the same size during follow-up. A clinically significant outcome was considered to have occurred in patients requiring secondary intervention for regrowth of the fragments or medical treatment for frequent symptomatic episodes. Univariate (Kaplan-Meier) and multivariate (Cox-regression) analyses were performed to determine significant predictors of the outcome. The mean follow-up was 31 months (range 6-80 months). Stone-free status, regrowth of fragments, and persistence of fragments of the same size were present in 21 (13.6%), 52 (33.8%), and 81 (52.6%) patients, respectively. A clinically significant outcome was documented in 75 patients (48.7%) as percutaneous nephrolithotomy was needed in 2, repeat SWL in 50, and medical treatment for symptomatic episodes in 23 patients. Significant independent predictors of a clinically significant outcome were fragment size > or =4 mm and history of recurrent stone disease (P < 0.001). The term "clinically insignificant residual fragments" is not appropriate for all patients with post-SWL fragments, as 48.7% of patients had fragments that became clinically significant. Fragments of 4 to 5 mm and recurrent stone disease predicted clinical significance.