Development of a new scoring system predicting medical expulsive therapy success on 4-10 mm distal ureteral stones: medical expulsive therapy stone score (METSS)

Ureteral stone passage by using medical expulsive therapy (MET) are affected by numerous radiological and clinical parameters. We aimed to construct a scoring system, which would be based on clinical and computed tomography (CT)-derived data, to predict the success of the MET approach. 186 patients presenting to urology clinic or emergency department with unilateral single 4-10 mm distal ureteral stone and who had MET were included. All patients were divided into two groups as the MET-successful group and the MET-unsuccessful group. The success rate of MET was 67.2%. Stone size >= 6.5 mm, stone density > 1078 HU, ureteral wall thickness (UWT) > 2.31 mm, ureteral diameter (UD) > 9.24 mm, presence of periureteral stranding (PUS) and presence of diabetes mellitus (DM) were stated as the independent risk factors. Based on the regression coefficients on multivariate logistic regression analysis, 1 point for stone size > 6.5 mm, 2 points for stone density > 1078 HU, 2 points for UWT > 2.31 mm, 3 points for UD > 9.24 mm, 1 point for presence of PUS and 1 point for presence of DM were assigned to patients for each risk factor. Higher medical expulsive therapy stone score (METSS) indicated lower MET success. All patients were classified into three risk groups according to METSS: low risk (0-3 points; success percentage: 92.8%); intermediate risk (4-5 points; success percentage: 60.4%) and high risk (6-10 points; success percentage: 8.3%). The METSS seems to separate successfully the patients with a favorable or adverse constellation of factors.