The bladder should be filled with more than 150mL of urine. The bladder is a urine storage organ, and when it fills up, the mucous membrane can be unfolded to detect lesions, and when it fills up with 150mL of urine, the mucous membrane of the bladder can be unfolded. Bladder capacity varies from person to person, usually the bladder capacity is more than 300mL, if the patient holds more than 300mL of urine, it will not affect the normal bladder function. When patients undergo urinary system, especially bladder examination, the bladder is required to be as full as possible, in order to facilitate the detection of disease, or the detection of bladder lesions. Therefore, patients can hold more urine, when there is an urgent need to urinate, that is, when the bladder capacity is more than 150mL or more, and then go to do the examination can be more accurate.