Stone size is only independent predictor of shock wave lithotripsy success in children: a community experience

We determined whether age, gender, body mass index, number of stones, stone location or total stone diameter could independently predict stone-free rates after extracorporeal shock wave lithotripsy in children.

We reviewed 149 patients 3 to 17 years old undergoing shock wave lithotripsy between 2001 and 2008. Cases were retrieved from a regional shock wave lithotripsy database. Variables analyzed included age, gender, body mass index, number of shocks delivered, stone location, number of stones and total stone diameter. Stone-free status on followup imaging at 2 weeks to 3 months was considered a successful outcome.

Of 149 patients 32 had multiple stones. After shock wave lithotripsy 106 patients (71%) were stone-free, 12 (8%) required a repeat procedure and 31 (21%) had residual fragments. Number of stones per patient ranged from 1 to 18 (mean +/- SD 2.14 +/- 2.60). Mean +/- SD number of stones was 1.87 +/- 2.42 in successfully treated patients and 2.81 +/- 2.92 in those with treatment failure (p = 0.065). Total stone diameter ranged from 2 to 90 mm (mean +/- SD 14.03 +/- 16.68). Mean total stone diameter was 11.1 +/- 13.4 mm in successfully treated patients and 21.3 +/- 21.4 mm in those with treatment failure (p <0.005).

To our knowledge we present the first multi-institutional cohort study in children demonstrating no significant relationship between successful outcome and patient age, gender, body mass index, stone location or number of stones. Only total stone diameter independently predicted shock wave lithotripsy success.