Ability of ESWL nomograms to predict stone-free rate in children

We aimed to evaluate whether the pediatric extracorporeal shock wave lithotripsy (ESWL) nomograms can predict stone-free status in children effectively and whether they are applicable to our series. We hypothesize that two current nomograms predicting successful treatment with ESWL in pediatric patients are valid.

We evaluated 415 renal units (children <18 years) with eligible data who received ESWL treatment for upper urinary tract stones. Children's age, gender, stone size, stone surface area, stone location and history of previous intervention were recorded. Children with no residual fragments after ESWL treatment were designated as stone-free. The nomograms described by Dogan and Onal were implemented to our series for the prediction of stone-free status.

Mean age of children was 64.7 ± 57.2 months. Male to female ratio was 219:196.78.8% (327) of children had single stone. Mean stone size was 10.0 ± 3.7 mm and mean stone surface area was 380.0 ± 72.2 mm². Our stone-free rate after single ESWL session was 52.5% (218/415). Mean residual stone size and stone surface area after single session was 6.4 ± 3.3 mm and 36.0 ± 44.2 mm² respectively. There were no significant difference between stone-free children and children with residual fragments regarding gender, age and history of previous intervention. Mean stone size and stone surface area in stone-free children were lower and lower pole stones had the lowest stone-free rate (p < 0.05). Area under curve for Dogan and Onal nomogram were 0.628 and 0.580 respectively in ROC analysis (0.05). The agreement between Dogan and Onal score was moderate in our series. In multivariate analysis only stone surface area and Dogan score found to be independent predictors of stone-free status (p < 0.05).

Only one study has assessed both nomograms in the literature. Both nomograms are reported to be independent predictors of stone free status. ROC analysis in our study revealed fair accuracy for both nomograms with higher area under curve for Dogan nomogram. Higher accuracy for both nomograms were reported by other authors. These nomograms offer practical data but more effective tools are needed to be developed for the prediction of stone-free status in pediatric ESWL.

Stone size and stone surface area are associated with stone clearance. Dogan and Onal nomograms can be useful in prediction of stone-free status in children. Dogan nomogram is superior to Onal nomogram.