Central stone density measured by computed tomography in Hounsfield units for predicting stone outcome after extracorporeal shockwave lithotripsy

Abstract

Background The density of the urinary stone is a determiner of extracorporeal shockwave lithotripsy (ESWL). It could be determined by computed tomographic (CT) measurement in Hounsfield units. In this study, we tried to establish an accurate way of stone density measurement by computed tomographic. Patients and methods In this prospective study, 18 patients with renal or upper ureteric stones were scheduled to perform ESWL. Stone densities were measured from different parts: central and peripheral measurements as well as stone size, location, and skin-to-stone distance. Results The patients' mean age was 40.4 ± 16.5 years. A total of 14 (77.8%) patients were male and four (22.2%) patients were female. The central density showed a statistically significant difference between the two groups with higher densities in the failed group (P = 0.001). The analysis proved that center density less than 935 HU predicts the successful outcome with a sensitivity of 71.4%, a specificity of 90.9%, a positive predictive value of 83.3%, a negative predictive value of 83.3%, and accuracy of 81.8%. Conclusion Central stone density is a significant predictor of the outcome of ESWL as higher density stone respond poorly to ESWL than low-density stone.