When inflammation, tumor or physiological changes occur in the uterus and parametrial tissues, tissue inflammatory exudate or leaky fluid in the concentration of the rectal trap of the uterus may be detected by ultrasonography after a certain amount is formed, suggesting pelvic effusion. Pelvic inflammatory disease refers to inflammation of the upper female genitalia and its surrounding tissues. The presence of pelvic inflammation does not necessarily mean that there is pelvic effusion, because in the early stage of inflammation, the infected tissues become degenerative and edematous lightly, and inflammatory exudation is not formed or the amount is very small, so it is impossible to detect pelvic effusion by ultrasound. If you have pelvic effusion, it does not necessarily mean pelvic inflammatory disease, nor does it necessarily require anti-inflammatory treatment. The female pelvis is influenced by the ovaries and the amount of fluid in the pelvis varies with the menstrual cycle. Therefore, whether pelvic effusion is pelvic inflammatory disease or whether anti-inflammatory treatment is needed should not rely only on ultrasound results, but must be combined with the patient’s medical history, clinical symptoms and signs.