Validation of a domestic nomogram for predicting shock-wave lithotripsy outcomes in children with urolithiasis

BACKGROUND: In 2024, the first Russian nomogram for predicting outcomes after the extracorporeal shock-wave lithotripsy (ESWL) in children was developed in the urological department of the National Medical Research Center for Children’s Health in Moscow, Russia. The nomogram is a mathematical relationship between several factors predicting ESWL outcomes. Such a model promotes a personalized and objective approach to the choice of treatment tactics for each patient. For further implementation of the developed nomogram into clinical practice, it is necessary to perform its external validation.

AIMS: to externally validate and assess the accuracy of the domestic nomogram for predicting the ESWL efficacy in children with urolithiasis.

METHODS: Dornier Compact Sigma device was used in all patients who underwent lithotripsy. The criterion of effective treatment was absence of stone fragments >3 mm in the urinary tract at ultrasound examination in 3 months after the surgery. Patients were divided into two groups depending on treatment outcomes. Then, a statistical analysis of the impact of various factors at lithotripsy outcomes was made. The prognostic accuracy of the previously developed nomogram was also evaluated.

RESULTS: A total of 86 renal units were included in the study. Patients’ average age was 12 years (6.25–15.00), female gender was predominant: 49 (57%) girls versus 37 (43%) boys. Lithotripsy was effective in 52.3%. A comparative analysis showed no statistically significant impact of patient’s gender (p=0.250) and age (p=0.839). When we compared multiplicity and accuracy of localization and their impact at ESWL effectiveness, we do found a statistically significant difference (p=0.010 and p=0.012, respectively). Size, volume, and density of the stone are the most significant predictors of ESWL outcome (p <0.001). The logistic regression analysis showed a statistical significance of summarized nomogram scores which may be used as an independent predictor of ESWL outcomes (p <0.001). Analysis of the confusion matrix showed that the nomogram sensitivity was 82.22%, specificity 78.05%, error-free 89.23%, accuracy 80.43%. Model F-measure was 0.81.

CONCLUSIONS: The performed external validation of the first Russian nomogram has confirmed its high predictive ability and clinical significance in assessing and predicting outcomes after extracorporeal shock wave lithotripsy in children with urolithiasis.