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

BACKGROUND: In 2024, the first Russian nomogram for predicting the outcome of extracorporeal shock-wave lithotripsy (ESWL) in children was developed in the urological department of the National Medical Research Center for Children’s Health. The nomogram represents a mathematical relationship between several factors, thus predicting the outcome of the operation, which allows 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 efficacy of ESWL in children with urolithiasis.

METHODS: A prospective non-randomized comparative study was conducted on a group of children under the age of 18 with renal calculi, who received treatment in the urological department of the National Medical Research Center for Children’s Health between January 2024 and September 2024. All patients underwent lithotripsy on the same Dornier Compact Sigma device. The criterion of treatment effectiveness was the absence of stone fragments >3 mm in the urinary tract according to the ultrasound performed 3 months after surgery. Depending on the success of treatment, the patients were divided into two groups, after which the statistical analysis of the influence of various factors on the outcome of the lithotripsy session was performed. The prognostic accuracy of the previously created nomogram was also evaluated.

RESULTS: A total of 86 renal units were included in the study. The mean age of patients was 12 years (6.25 - 15.00), female gender was predominant: 49 (57%) girls versus 37 (43%) boys. The efficacy of lithotripsy was 52.3%. In the comparative analysis, there was no statistically significant effect of gender (p = 0.250) and age (p = 0.839) of the patients on the outcome of ESWL. When comparing the multiplicity and accuracy of localization as a function of the success of the ESWL session, we found statistically significant differences (p = 0.010 and p = 0.012, respectively). Size, volume, and density of the stone remained the most significant predictors of success (p < 0.001). Logistic regression analysis proved the statistical significance of the sum of the nomogram scores and the possibility of its use as an independent predictor of the success of the ESWL session (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%. The F-measure of the model was 0.81.

CONCLUSIONS: External validation of the first Russian nomogram confirmed its high predictive ability and clinical significance in assessing the probability of success of extracorporeal shock wave lithotripsy in children with urolithiasis.