Some ultrasound items, such as ultrasound examination of the urinary tract, uterine adnexa, prostate, etc. need to hold urine, while other ultrasound generally do not need to hold urine. Urinary ultrasound need to hold urine, because only in the case of a full bladder can clarify the situation inside the bladder, if you do not hold urine can not improve the relevant examination. Prostate ultrasound and transabdominal ultrasound of the uterine adnexa also need to hold urine in order to check clearly. In addition, if the bladder residual urine volume is measured, in addition to holding the urine, it is also necessary to determine the bladder residual urine volume again after urination. Other ultrasounds, such as abdominal ultrasound, thyroid ultrasound, cardiac ultrasound, and vascular ultrasound, do not require urine holding.