Outcome of small residual stone fragments following shock wave lithotripsy in children

Purpose: We evaluate the outcome of small residual stone fragments (RF) following extracorporeal shock wave lithotripsy (ESWL, Dornier Medical Systems, Inc., Marietta, Georgia) in children. Materials and Methods: The medical records of 39 boys and 44 girls (88 renal units) with urolithiasis who underwent ESWL were reviewed. Median patient age was 7 years. Average stone burden was 14 mm. Mean followup was 46 months. After the first ESWL 40 of the 88 (46%) renal units became stone-free and 18 (20%) had RF 5 mm or less. The remaining 30 (34%) units required further treatment using ESWL or ancillary surgical procedures that rendered 12 of them stone-free and 8 with RF. The 26 renal units with RF constitute our study subjects. Adverse outcomes such as growth of RF, symptomatic episodes or calculi recurrence in stone-free cases were recorded. Results: Of the 26 renal units with RF 5 mm or less, 18 (69%) had an adverse clinical outcome (symptoms or RF growth) and 8 (31%) patients were asymptomatic and had no stone growth. Patients with RF had a significant increase in adverse clinical outcome compared to stone-free subjects, with an odds ratio of 3.9 (95% CI 1.5-9.6). The presence of metabolic disorders was associated with RF growth (odds ratio 11.4, 95% CI 1.5-79). Conclusions: Small RF after ESWL is clinically significant in children and increase the chance of adverse clinical outcome. These patients require close followup, particularly those with identifiable predisposing disorders.