OBJECTIVETo evaluate the factors affecting the efficacy of extracorporeal shock wave lithotripsy (ESWL) and establish a model for predicting the success rate of a single ESWL session in the treatment of single renal calculus.

METHODSBetween January 2008 and February 2010, 325 patients underwent ESWL monotherapy and were followed up for at most 3 months. The correlations between the outcome of a single ESWL session and the patients' age, gender, body mass index (BMI), disease duration, pretreatment renal colic, hematuria, urinary irritation symptoms, stone location, stone laterality, stone length and stone width were analyzed. The statistically significant factors identifies were further analyzed by multivariate logistic regression, and the predictive model was established.

RESULTSThe stone-free rate of ESWL was 76.9%. Univariate analysis found that the patients' age, stone laterality, stone location, disease duration, pretreatment hematuria, stone length and width all significantly affected the outcome of the treatment. Logistic regression analysis indicated the factors including disease duration, pretreatment hematuria, stone length and stone width determined the success rate of the treatment. Hosmer and Lemeshow Test showed a good fitting of the predictive model (Χ(2)=18.144, df=8, P=0.168) with an overall accuracy of 87.4%.

CONCLUSIONDisease duration, pretreatment hematuria, stone length and width are independent factors affecting the outcome of a single ESWL session for single renal calculus.