Kidney stone 4mm, the size is equivalent to a green bean. Generally, stones below 4mm can be discharged on their own without the use of extracorporeal shock wave lithotripsy or surgery, medication and other treatment methods, by drinking more water and urinating more often, most of the stones can be discharged on their own. However, stones located in the lower renal calyces can exist for a long time. Stones in the lower renal calyces are not easily discharged through the ureter, so they may exist for a long time and need to be reviewed regularly. Stones in the upper and middle calyces of the kidney are easily expelled and most of them can be expelled by themselves after drinking water and being active. Sometimes, stones from the kidneys can be discharged into the ureter and stay somewhere in the ureter, causing obstruction of the ureter and immediate pain.