Wiesenthal JD et al, 2011: A clinical nomogram to predict the successful shock wave lithotripsy of renal and ureteral calculi
Wiesenthal JD, Ghiculete D, Ray AA, Honey RJ, Pace KT
Division of Urology, Department of Surgery, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
PURPOSE: Although shock wave lithotripsy is dependent on patient and stone related factors, there are few reliable algorithms predictive of its success. In this study we develop a comprehensive nomogram to predict renal and ureteral stone shock wave lithotripsy outcomes.
MATERIALS AND METHODS: During a 5-year period data from patients treated at our lithotripsy unit were reviewed. Analysis was restricted to patients with a solitary renal or ureteral calculus 20 mm or less. Demographic, stone, patient, treatment and 3-month followup data were collected from a prospective database. All patients were treated using the Philips Lithotron® lithotripter.
RESULTS: A total of 422 patients (69.7% male) were analyzed. Mean stone size was 52.3±39.3 mm2 for ureteral stones and 78.9±77.3 mm2 for renal stones, with 95 (43.6%) of the renal stones located in the lower pole. The single treatment success rates for ureteral and renal stones were 60.3% and 70.2%, respectively. On univariate analysis predictors of shock wave lithotripsy success, regardless of stone location, were age (p=0.01), body mass index (p=0.01), stone size (p<0.01), mean stone density (p<0.01) and skin to stone distance (p<0.01). By multivariate logistic regression for renal calculi, age, stone area and skin to stone distance were significant predictors with an AUC of 0.75. For ureteral calculi predictive factors included body mass index and stone size (AUC 0.70).
CONCLUSIONS: Patient and stone parameters have been identified to create a nomogram that predicts shock wave lithotripsy outcomes using the Lithotron lithotripter, which can facilitate optimal treatment based decisions and provide patients with more accurate single treatment success rates for shock wave lithotripsy tailored to patient specific situations.
Copyright © 2011 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.
J Urol. 2011 Aug;186(2):556-62. doi: 10.1016/j.juro.2011.03.109
PMID: 21684557 [PubMed - indexed for MEDLINE]
The important predictive factors for successful treatment of renal stones were stone size, patient age, skin-to-stone distance. For ureteral stones BMI and stone size were identified as predictors.
The formulated equations are based on treatments apparently carried out in a standardized way, with general anaesthesia and at a shockwave frequency of 120. Most patients will today be treated without general anaesthesia and with shockwave frequencies lower than 120.
Whether a detailed mathematical summary of the variables is easier to work with than by just looking at the patient and the stone situation is of course a matter of personal preference. For the individual patient, however, there might be other factors that determine whether one or several treatment sessions will be necessary. One point that needs to be considered thus is if a re-treatment should be considered as failure.
The predictive factors discussed in this article undoubtedly can be used as a guide to predict the outcome, but also to get an idea in whom and in which way the treatment strategy should nor can be individualized.