[Evolution of urinary lithiasis composition in a Spanish health care area over the last four decades].

Objective: To provide an updated epidemiological description of urinary lithiasis in a health area in the Western hemisphere over the past four decades.

Methods: 2704 urinary lithiases analysed in our institution between 1980 and 2015 were retrospectively reviewed. They were analyzed using polarized light microscopy, and in the case this method had questionable results we used X-ray diffraction. The variables collected were the lithiasis chemical composition (oxalates, phosphates, uric acid, infectious, cystine, mixed, other). Regarding the date of the analysis, the series of cases was grouped into four periods (1980-1989, 1990- 1999, 2000-2009, and 2010-2015), and also by sex and age of the patient.

Results: The mean age at diagnosis was 48.32 years (49.37 in men vs 46.53 in women, p=0.005). A male predominance was found (58.7%). Throughout the four decades, the involvement of women has progressively diminished compared to men. Of all the lithiases, the most frequent were those composed of oxalates (43.3%), followed by uric acid (16.9%) and infectious types (10.7%). The uric acid and oxalate lithiases were more common in men than in women (67.4% vs. 32.6% and 59.1% vs. 40.9%, respectively, p<0.001), while the lithiasis of infectious origin was more frequent in women than in men (56.3% vs. 43.7%, p<0.001). Throughout the time period, a trend of increasing oxalic lithiases and decreasing uric acid and phosphate lithiases was observed, as well as an increase of infectious lithiases over the past five years.

Conclusions: In our setting, urinary lithiases appear more frequently in males at the end of the fourth decade of life. The most common lithiases are composed of oxalates, and their frequency has increased over time, while uric acid and phosphates lithiases have decreased.