The factors influencing upon stone fragmentation by extracorporeal shock wave lithotripsy (ESWL) of ureteral stones are considered to be stone size, location, component, and impaction. ESWL was performed in 322 cases with ureteral stones using
the
Modulith SL 20 electromagnetic lithotripter between December 1990 and July 1992. The factors influencing upon stone fragmentation such as stone size, location, degree of hydronephrosis, shape, pain character and presence or absence of urinary
tract
infection for the first and second session of ESWL were investigated.
The failure rate of ESWL according to stone size was similar for stones smaller than 2.0cm(p>0.05) but was high for stones larger than 2.0cm(p<0.05). The failure rate of ESWL for upper ureteral stones was similar to midureteral stones(p>0.05) but
was
low for lower ureteral stones(p<0.05). The failure rate of ESWL according to degree of hydronephrosis was similar in cases without hydronephrosis and with mild hydronephrosis (p>0.05) but was high in cases with severe hydronephrosis(p<0.05). The
failure
rate of ESWL according to stone shape was not significantly different(p>0.05). The failure rate of ESWL in cases without pain was not significantly different from in cases with dull or colic pain(p>0.05). Urinary tract infection did not influence
on the
failure rate of ESWL (p>0.05).
From this study it is believed that factors affecting fragmentation of ureteral stones were stone size, location, and degree of hydronephrosis, but stone shape, presence of absence of pre-ESWL pain or urinary tract infection did not influence on
stone
fragmentation rate.
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