Objectives: To evaluate the role of different stones criteria in non-contrast multi-detector computed tomography (MDCT) in predicting successful outcome following extracorporeal shock wave lithotripsy (ESWL) for urinary calculi.
Methods: 120 patients who underwent ESWL as a primary treatment for renal or ureteric calculi were included from May 2014 to July 2015. Different criteria of stones were assessed by MDCT before ESWL including location, size, Hounsfield unit density, skin-to-stone distance. Patients were followed up for 3 months to assess stone clearance. The effect of different Ct criteria on stone clearance was analysed using Chi-Square test or Fisher-Exact tests. ROC (receiver operating characteristic) curve was used to determine the cut-off for stone density.
Results: Stone size was a statistically significant factor for ESWL success with a stone free rate > 95% for renal stones < 2 cm (p < 0.001). The mean stone density for cases with ESWL success was 662.56 ± 281.3 HU while it was 1097.54 ± 186.3 HU for cases with failed ESWL. The efficiency of ESWL was reduced when SSD was more than 10 cm with a stone free rate < 82%.
Conclusion: Stone size, density, site and SSD affect ESWL outcome which is improved with shorter SSD, stones < 2 cm and density below 1059 HU. MDCT provides accurate estimation of these factors.