Extracorporeal shockwave lithotripsy; which parameter determines the outcome: calculus radiodensity or calculus size

ABSTRACT

To evaluate the effect of urinary calculi attenuation values from non enhanced computed tomography [stone radiodensity] and stone size in determining the outcome of treatment by ESWL. Descriptive case series study. Department of Diagnostic Radiology, Lahore General Hospital Lahore, in collaboration with the Department of Urology, Lahore General Hospital Lahore. Study was carried out over a period of six months from January 2012 to July 2012. Seventy patients with solitary renal calculus of 05 mm - 20 mm size were evaluated for calculus attenuation values in Hounsfield Units on non enhanced computed tomography. Patients were being grouped according to calculus attenuation values as 1] less than 500 HU [soft] 2] 500-1000 HU [medium] 3] more than 1000 HU [Hard]. Patients were also distributed in three groups according to stone size as 1] 5-10 mm 2] 11-15 mm 3] 16-20 mm. Patients were being subsequently treated with ESWL. During each ESWL session 3000 shockwaves were given. Stone clearance was documented by USG within three month after start of treatment. Out of 70 patients stones were cleared in 84.3% [n=59] patients. According to the stone density, the rate of stone clearance was 100% [n=19] in group 1, 88.9% [n=27] in group 2 and 66.7% [n=24] in group 3. Regarding the stone size, stones were cleared in 88.9% [n=9] in group 1, 77.4% [n=31] and 90% [n=30] in group 3. The best outcome was in patients with stone diameter of 16-20 mm and a density of < 500 HU. The worst outcome was in patients with stone diameter of 11-15 mm and a density of >1000 HU. The attenuation value of stone has a greater impact on ESWL outcome than the stone size. Further these attenuation values of urinary tract stones before ESWL helps in determining the treatment outcome and in planning alternative treatment in patients with likelihood of poor outcome from ESWL