Background: The changes over time of the annual incidence of lower urinary
tract stones in Japan from 1965 to 1995 were analyzed.
Methods: Data on lower urinary tract calculi were abstracted from the past
three nationwide surveys of urolithiasis, which covered nearly all major ho
spitals and urologists in Japan and enumerated all outpatient visits diagno
sed as urolithiasis in the years 1965, 1975, 1985 and 1995. Chronological c
hanges in the sex- and age-related annual incidences of lower urinary tract
stones and stone composition were estimated.
Results: Lower urinary tract stones were predominant in men 60 years of age
or older. Between 1965 and 1995, the annual incidence has significantly de
creased in men greater than or equal to 60 years of age from 37.2 to 27.0 p
er 100 000 and significantly increased in women greater than or equal to 60
years of age from 2.4 to 4.8 per 100 000. In men, an increased proportion
of uric acid and calcium stones as well as a decreased frequency of infecti
on stones is a phenomenon common to upper urinary tract stones. However, in
fection and calcium stones have been two major stone types in women.
Conclusions: In contrast to upper urinary tract calculi, the incidence of l
ower urinary tract stones has decreased over the last 30 years in men great
er than or equal to 60 years of age predisposed to this disease.