Urinary stones are excreted by urination, especially for stones smaller than 6 mm, and most of them can be excreted by urination if they have a smooth surface and no burr-like changes. There are actually more small crystals in human urine. Because of their small size, patients do not have any conscious symptoms during the process of excreting small crystals, but when urine is collected for urine sediment examination, the number of crystals can be seen to increase significantly. When the crystals fuse and increase in size further, stones are formed, which then cause pain during the process of expulsion. If the stones are too large and become lodged in the urinary system causing hydronephrosis or obstruction, they can cause acute pain. However, for small stones or stones with a smooth surface, most of them can be expelled when drinking more water and urinating more often.