It is sometimes necessary to hold your urine when doing a renal ultrasound because while holding your urine the bladder fills up and can be differentiated from the uterus to further find the ureters and kidneys, which can be visualized. Urine holding is required for both uterine adnexal ultrasound and urologic CT, and is necessary to diagnose the disease. When the patient has obvious urinary frequency, urgency or incontinence, it is not possible to hold the urine, and the renal ultrasound can not be performed, and the structure of the kidneys can be clarified by the abdominal standing flat film. If the patient has kidney stones, they can be visualized under color ultrasound, but not under abdominal standing plain film, and the examination is limited. When abdominal ultrasound is done, it can also show the condition of the kidneys, and there is no need to hold urine at this time.