Many women experience pelvic effusion, a gynecologic pelvic effusion usually refers to the presence of some fluid in the pelvic cavity as indicated by ultrasound during an ultrasound examination. Pelvic fluid is usually present in the rectal sunken recess of the uterus, the Douglas fossa, because that is the lowest part of the woman’s body. If the amount of pelvic fluid is not large and there are no uncomfortable symptoms, most of them are physiological and can be absorbed on their own. This is because fluid exists in the pelvic and abdominal cavities of the human body, and during ovulation, a small amount of follicular fluid flows into the pelvic cavity at the same time when the follicles are discharged, and this fluid accumulation in the lowest part of the body is completely normal and does not require any treatment. However, if the amount of pelvic fluid is large, accompanied by symptoms such as abdominal pain, bloating, abdominal lumps, lumbosacral discomfort, fever, and purulent leukorrhea, it is necessary to further examine what the cause is. Common pathological causes include inflammatory exudation from the pelvic and abdominal cavities, bleeding in the pelvic and abdominal cavities such as miscarriage or rupture of ectopic pregnancy, ascites caused by malignant tumors of the ovaries, etc. In short, there are two kinds of causes for pelvic effusion, physiological and pathological. If it is physiological, there is no need to be nervous and no need for treatment; for pathological, the cause should be found and treated in time.