Transvaginal gynecologic ultrasound usually does not require fasting, but when transabdominal ultrasound is performed it is necessary to hold urine in preparation. The upper abdominal tissues and organs usually need to be prepared on an empty stomach. This is because after eating, bile secretion and gallbladder contraction will occur, and the gastrointestinal tract will accelerate peristalsis and produce a large amount of gas, which will obscure or affect the display of the surrounding tissues and organs and prevent the purpose of the examination. Gynecological examination is mainly located in the lower abdomen and organs in the pelvic cavity, and the gas in the intestinal tract will still have a relatively large impact on it. Moreover, the uterus and the adnexal area are located just behind the bladder, so it is usually necessary to fill the bladder when doing a gynecological ultrasound, which is what people call holding urine. A full bladder pushes the bowel around the uterus and adnexa, allowing the uterus to be better displayed. A full bladder is also a good window for sound transmission, allowing a clearer image of the uterine appendages to be displayed. However, for people with particularly large amounts of feces in the intestinal canal, it is still recommended to have a bowel movement before performing the ultrasound. It is not necessary to fast during a gynecological abdominal ultrasound, but it is necessary to hold urine and empty the bowels.