Renal cysts are a general term for cystic lesions that appear in the kidney and do not communicate with the outside world. The cause of the disease is complex and not yet well understood. For simple renal cysts with slow progression and good prognosis, those without conscious symptoms or compression and obstruction do not need surgical intervention, nor do they require oral medication, and do not affect daily life, and can be reviewed by ultrasound once every six months or once a year. For simple kidney cysts larger than 4 cm in diameter, rapidly increasing cysts or malignant kidney tumors, they need to be seen in hospital as soon as possible. Polycystic kidney should also be seen as soon as possible.