Kidney stones >4mm may cause hematuria, and the larger the stone, the higher the probability of causing hematuria. When there is a stone >4mm in the kidney, it can cause the mucous membrane to break down during the flow with urine causing bleeding. In this case, the bleeding is often small and the red color of the urine cannot be seen with the naked eye, but an increase in the number of red blood cells can be seen when the urine is taken for microscopic observation. If the size of the stone increases further, the bleeding will increase further, and the redness of the urine can be detected by the naked eye, which is called carnal hematuria. Patients need to go to the hospital for examination to clarify the location of the stone, and then extracorporeal shock wave lithotripsy or medication is recommended to promote stone discharge, and the hematuria will disappear. When the kidney stone is >2cm, surgery is needed to remove the stone from the body in order to clear the lesion and stop the hematuria.