Predictive factors and treatment outcomes of Steinstrasse following shock wave lithotripsy for ureteral calculi: A Bayesian regression model analysis

PURPOSE: This study aims to assess the predictive factors and treatment outcomes of Steinstrasse formation following shock wave lithotripsy (SWL) for ureter stone. MATERIALS AND METHODS: The medical records of 1,418 ureter stone patients who underwent one-session SWL from November 2005 to May 2013 at our medical institute were retrospectively reviewed. Finally, 551 patients met inclusion criteria. Maximal length and location of stone, stone attenuation (Hounsfield units), and skin-to-stone distance (SSD) were determined on pretreatment non-contrast computed tomography. RESULTS: Of 551 patients, 12 patients (2.2% of total cohort) developed Steinstrasse after one-session SWL. The Steinstrasse incidence was significantly associated with stone size, stone attenuation value, and SSD. Prophylactic ureter stenting was not a statistically significant predictor of Steinstrasse formation. After propensity-score matching, Steinstrasse group showed a significant shorter SSD compare to non-Steinstrasse group. Multivariate logistic regression and Bayesian analysis revealed that stone size, stone attenuation and SSD were significant predictor of Steinstrasse formation following SWL for ureter stone. The Steinstrasse resolved spontaneously in six patients and remaining six patients were treated by additional SWL. None of patients with Steinstrasse required ureteral stenting, percutaneous drainage, or consequent surgical intervention. CONCLUSIONS: Steinstrasse formation following SWL for ureter stone was rare event but nonnegligible. Large stone size, high stone attenuation and short SSD were significant predictors of Steinstrasse formation following SWL for ureter stone. Majority of patients with Steinstrasse formation could be treated conservatively in this clinical scenario.