RESUMEN
To evaluate the usefulness of urinary calculi attenuation values from non-contrast computed tomography [NCCT] in predicting the outcome of treatment by extracorporeal shock wave lithotripsy [ESWL]. Between 1[st] January 2007 and 30[th] June 2008, we evaluated 178 patients undergoing ESWL for solitary urinary calculi. All patients had NCCT at 120 Kv and 240mA on a helical CT scanner. During each ESWL session 3000 shock waves were given to a maximum of 3.0Kv.A final plain X-ray of the kidney, ureters and bladder was taken 12 weeks after the last ESWL session. Fragments of /= 750HU, 52 [84%] needed three or fewer ESWL sessions and 57[92%] had complete clearance. Of patints with calculi of>750HU, 40 [74%] required three or more ESWL sessions, and 32[60%] had complete clearance. The best outcome was in patients with calculus diameters of<1.1 cm and mean densities of 750HU and diameter of > 1.1cm; 18[75%] needed three or more ESWL sessions and the clearance rate was only 50%. The calculus density was a stronger predictor of outcome than size alone The HU measurement of urinary calculi [stone density] on pretreatment non contrast CT predicts the stone free rates after ESWL. This might help in planning alternative treatment in patients with a probable poor outcome, and to increase the efficiency of ESWL, thus decreasing the cost of treatment