You must hold your urine for a gynecological ultrasound because the only way to see the exact location of the uterus and adnexa is to hold your urine. The uterus and bladder are very close together, and it is difficult to tell which one is the uterus without holding your urine. Under ultrasound the full bladder will reflect the light through the abdominal organs, before doing ultrasound, you need to get up in the morning to urinate and defecate, and then drink water before the examination. Frequent holding of urine increases the pressure in the bladder, which can lead to cystitis and even rupture. When doing ultrasound, it is brief and usually does not cause any effect.