Prevalence and Epidemiologic Characteristics of Lower Urinary Tract Stones in Japan

ObjectivesTo analyze the changes in the annual incidence and epidemiologic details of lower urinary tract stones in Japan, a nationwide survey of urolithiasis was performed.MethodsData were obtained from all patients who had been diagnosed by urologists in 2005 as having lower urinary tract stones, including both first and recurrent stones. The data were separately enumerated according to hospital size, irrespective of admission and treatment. The study included all hospitals approved by the Japanese Board of Urology and thus covered nearly all urologists practicing in Japan. The estimated annual incidence according to sex, age, and stone composition was compared with other nationwide surveys taken from 1965 to 1995.ResultsThe incidence of lower urinary tract stones in Japan has steadily increased from 4.7/100 000 in 1965 to 9.1/100 000 in 2005. However, the age-standardized annual incidence of lower urinary tract stones in Japan decreased slightly from 5.5/100 000 in 1965 to 5.4/100 000 in 2005. The incidence of stones containing calcium has significantly increased from 50.7% to 72.0% among men and the incidence of infection-related stones has decreased significantly from 26.2% to 10.1%. The ratios of uric acid calculi in men and of infection-related stones in women increased with age.ConclusionsThe increased incidence of lower urinary tract stones is in slight contrast to the sudden increase in the incidence of upper urinary tract stones, which might be associated with the aging of the Japanese population.