Are the current nomograms sufficient to predict shockwave lithotripsy outcomes?

Introduction And Objectives: To investigate factors affecting SWL outcomes, validate three current nomograms (Kim JK, Triple D and S3HoCKwave) and compare the predictive ability of the nomograms for SWL outcomes in upper urinary tract stones.

Patients And Methods: Medical records of patients with renal and proximal ureteral stones treated with SWL between March 2013 and October 2020 were retrospectively reviewed. Factors affecting SWL success were analyzed with multivariate logistic regression analysis and the three predictive scoring systems compared with the area under the curve (AUC).

Results: A total of 580 patients were included in our study. The overall stone free rate was 61% and 144/580 patients (24.8%) were stone free after one session. In multivariate logistic regression analysis, stone location at upper calyx (OR:2.988; 95%Cl: 1.350-6.612; p = 0.007), middle calyx (OR:3.036; 95%Cl: 1.472-6.258; p = 0.003), and lower calyx (OR:2.131; 95%Cl: 1.182-3.839; p = 0.012), as well as number of stones (OR:1.663; 95%Cl: 1.140-2.425; p = 0.008), maximum diameter of stone (OR:1.156; 95%Cl: 1.098-1.217; p < 0.001) and maximum Hounsfield Unit (OR:1.001; 95%Cl: 1.001-1.002; p < 0.001) were independent risk factors of SWL failure. The AUCs of the Kim JK, Triple D and S2HoCKwave scores for predicting SWL success were 0.678, 0.548, and 0.626 respectively.

Conclusions: Stone location, number, maximal diameter, and maximum HU were independent predictive factors for SWL outcome in the treatment of upper urinary tract stones. Current nomograms, "Kim JK nomogram", "Triple D score" and "S3HoCKwave score" can predict treatment success after SWL, but all of them have poor discrimination according to AUC analysis.