Urinary stones can occur at any age, but the peak age of incidence is between 25 and 40 years. Recent statistics show that the incidence of urolithiasis has a tendency to increase with age. In men, the peak age is between 30 and 50 years; in women, there are two age peaks, 25 to 40 and 50 to 65 years. The reasons for the second peak in women may be related to the following factors: (1) postmenopausal osteoporosis and decrease in estrogen, which leads to increased reabsorption of bone calcium and causes hypercalciuria; (2) decreased excretion of citrate in the urine. Relatively few people develop urolithiasis before the age of 20. Most stones in children occur between the ages of 2 and 6 years and are often associated with genetics, infection, malformation, and malnutrition. With the aging of the population, the number of elderly men with prostatic hyperplasia combined with bladder stones is also gradually increasing. In general, there are more men than women with urolithiasis, and the ratio of men to women is (2~3):1. According to statistics, the ratio of men to women with upper urinary tract stones is similar, and men to women with lower urinary tract stones is significantly higher, reaching (3.7~5.3):1. The reasons for the higher incidence of urinary tract stones in men than in women may be related to the following factors: ① The anatomical structure of the urinary tract is different between men and women, and the urethra is wider and shorter in women, so it is less likely to occur. urinary retention. (2) There are differences in the dietary habits (amount and composition of diet) and working environment between men and women. ③Androgens have the effect of increasing the formation of oxalic acid; while estrogens can not only increase the excretion of citrate in urine, but also inhibit the activity of parathyroid hormone and reduce the concentration of blood and urine calcium. Citrate readily forms soluble complexes with calcium, increasing the solubility of calcium salts and therefore reducing the chance of urinary stone formation. ④ Protective colloids are increased in the urine of pregnant women. In recent years, the number of women with urolithiasis has increased more rapidly than men, and the reasons for this are mainly related to diet and lifestyle patterns. The latest data from the United States show that the ratio of men to women with urolithiasis has developed from 1.7:1 in 1997 to 1.3:1 in 2002, which is mainly related to the increase of kidney stones and ureteral stones in women, but also to the predominance of obesity and overweight in women. Obese women have a higher risk of developing urolithiasis than obese men.