[Epidemiology of urinary lithiasis in our Unit. Clinical course in time and predictive factors]

To analyze the incidence of lithiasis and stone composition in our setting. The trend is compared with the results of the majority of studies on urinary calculi reported in the literature based on the number and composition of stones.

The study comprised patients referred to the Urolithiasis Unit of our hospital over the last 21 years. Stone composition was analyzed by infra-red spectroscopy. The study period was divided into 4 time intervals: 1977-1979, 1977-1980, 1977-1987 and 1977-1998 in order to determine the trends of the incidence of lithiasis in our setting.

A total of 5516 patients were reviewed; of these, 766 had recurrence. The distribution was 385, 995, 3378 and 5516, respectively. Calcium oxalate calculi showed an incidence of 61.3%, calcium phosphate 18.5%, uric acid 11.2%, infectious calculi (ammonium urate and ammonium magnesium phosphate) 6.6%, and finally the incidence of cysteine calculi was 0.77%. Concerning the distribution according to sex, 62% of the males had calcium oxalate stones, 68% uric acid, 42.5% phosphate and 45% infectious lithiasis. The trends for uric acid, infectious, oxalate and phosphate calculi changed over time.

There is a clear trend of calculi prevalence in the male, particularly oxalate and uric acid calculi. There is a trend for cysteine calculi to remain the same, calcium phosphate and oxalate calculi to increase, and uric and infectious calculi to decrease. The changes observed may be due to dietary changes and improvement in the quality of life.