Extracorporeal shockwave lithotripsy for renal stones in pediatric patients: a multivariate analysis model for estimating the stone-free probability.

OBJECTIVES: To define factors affecting the stone-free rate of extracorporeal shockwave lithotripsy in the treatment of pediatric renal calculi, and to establish a regression model for pretreatment prediction of stone-free probability. METHODS: From January 1999 through February 2012, 207 children with mean age 6.4 ± 3.8 years underwent shockwave lithotripsy with Dornier Lithotripter S for treatment of renal stones. The stone-free rate was evaluated 3 months after the last shockwave lithotripsy session with non-contrast computed tomography. Treatment success was defined as complete clearance of the stones with no residual fragments. Multivariate logistic regression analysis was used to identify independent risk factors and to predict the probability of being stone free. RESULTS: The mean length of the stone was 11.6 ± 4 mm. The stone-free rate was 71%. Independent factors that adversely affect stone-free rate were increasing stone length and calyceal site of the stone. Relative risks for not being free of stones were 1.123 for stone length, 2.673 for stones in the upper or middle calyx and 4.208 for lower calyx stones. CONCLUSION: Stone length and location are prognostic factors determining stone-free rate after shockwave lithotripsy for renal calculi in pediatric patients. Based on our analysis, shockwave lithotripsy should be recommended for renal pelvis stones up to 24 mm, upper or middle calyceal stones up to 15 mm and lower calyceal stones up to 11 mm.