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.
Keywords: Non-contrast computed
tomography, Shock wave lithotripsy,
Urinary calculi.