If a kidney stone causes painful urination, the possible causes are as follows: 1. If a kidney stone is discharged into the urethra and causes painful urination, it is necessary to go to the hospital for examination to clarify whether the stone has been discharged, and if necessary, urethroscopy is needed to understand whether the stone is stuck in the urethra and cannot be discharged and causes pain. 2. If a kidney stone is combined with infection, it can cause painful urination, which is accompanied by frequent urination, urgent urination or In this case, in addition to painful urination, it is accompanied by frequent urination, urgent urination or bleeding in urination. Ultrasound examination of the urinary system is needed to identify changes in the location of the stones, and routine urine tests and urine culture tests are needed to confirm the presence of infection. If infection is present, the painful urination is due to the combination of stone and infection.3. The painful urination is caused by the irritation of the mucous membrane of the urethra during the discharge of the stone.