EXTRACORPOREAL SHOCKWAVE LITHOTRIPSY

WHICH PARAMETER DETERMINES THE OUTCOME: CALCULUS RADIODENSITY OR CALCULUS SIZE

Abstract

Objective: 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. Study design: Descriptive case series study. Setting:
Department of Diagnostic Radiology, Lahore General Hospital Lahore, in collaboration with the
Department of Urology, Lahore General Hospital Lahore. Duration of study with dates: Study
was carried out over a period of six months from January 2012 to July 2012. Subjects and
Methods: 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.
Results: 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. Conclusions: 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.