One hundred patients who have a ureteral stone lesser than 1.0cm in diameter were evaluated for spontaneous passage during 8 months between July, 1991 and February, 1992. The spontaneous passage in accordance with duration of follow-up, the stone
site,
size, shape and degree of ureteral obstruction was investigated. The overall rate of spontaneous passage was 56.0% with the duration of 39.3 days ranging from 2 days to 8 months. Among these 56 patient, 48(85.7%) obtained a spontaneous passage
within 8
weeks. The rate and duration of spontaneous passage according to stone site were 57.7%, 67.4 dyas in upper ureter, 25.0%, 64.0 days in mid ureter and 57.1%, 21.9 days in lower ureter, respectively. Spontaneous passage rate was insignificantly
correlated
with the increment of stone size, but the duration requiring for spontaneous passage of lower ureteral stone was shorter than those of upper or mid ureteral stones. For stone shape the smooth surface or cylindrical shaped stone was more easily
passed
out spontaneously than the irregular or round shaped one. And, the severer ureteral obstruction, the poorer spontaneous passage was observed. Threrefore, the ureteral stone which is smaller than 1.0cm in diameter could be expected a spontaneous
passage
for 8 weeks at least unless there are specific symptoms or impairment of renal function, especially when the stone has smooth-cylindrical shape and the ureter shows minimal obstruction.
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