The formation mechanism and causes of urinary calculi are complex. The common reasons are as follows: 1. Abnormal metabolism. The body has abnormal metabolism of calcium, oxalic acid, uric acid, cystine, etc., which leads to the increase of urine content or the decrease of solubility, crystal precipitation, and the formation of stones. 2. Urinary system factors, renal injury, renal calcification, urinary tract infection, obstruction and foreign bodies can also lead to stone formation. 3. Drug related factors: drugs with high concentration and low solubility in urine, such as nifedipine, indinavir, etc. These drugs themselves are components of stones.