Many times I see patients with gynecological ultrasound sheets and ask: “Look, doctor, the ultrasound sheet says there is pelvic fluid. Then the patient asks with a series of questions: Why do I have pelvic fluid? Is it serious? Do I need treatment? Does it affect pregnancy? I was told that my pelvic inflammatory disease is very serious, do I need an injection? …… is here to give you an overview of pelvic fluid. The pelvic cavity is the lowest part of the abdominal cavity in the body, and under physiological conditions, there is a small amount of fluid in the pelvic cavity, which mainly plays a lubricating role, generally not more than 50 ml. pelvic fluid can be divided into physiological pelvic fluid and pathological pelvic fluid. Physiological pelvic fluid mostly occurs in women after ovulation or during early pregnancy and can be absorbed naturally without treatment. Pathological pelvic effusion is mostly caused by inflammation, and the effusion is inflammatory exudate, which mainly needs antibiotic treatment. Most common clinical pathological pelvic effusions are caused by pelvic inflammatory diseases, including endometritis, tubal inflammation, tubo-ovarian abscess and pelvic peritonitis, mainly related to patients’ poor hygiene habits, such as multiple sexual partners, too frequent sexual intercourse, lower genital tract infections (Neisseria gonorrhoeae, Chlamydia, pathogenic bacteria infecting the genital tract), menstrual intercourse, and after surgical operations in the uterine cavity (sexual intercourse within one month after delivery, after surgery (within one month after delivery, after surgery, etc.). Pelvic effusion caused by acute and chronic pelvic inflammatory disease and adnexitis is associated with symptoms such as fever, increased vaginal discharge, lower abdominal distension, lumbosacral pain, anal cramping, increased blood count, cervical pain or uterine pressure or adnexal pain on gynecological examination. If pelvic inflammatory disease is not treated timely and thoroughly, sequelae of pelvic inflammatory disease may occur, which can lead to infertility, tubal pregnancy (ectopic pregnancy), chronic pelvic pain, and recurrent inflammation, which can seriously affect women’s reproductive health. Therefore, for the sake of women’s health, please pay attention to sexual hygiene to reduce sexually transmitted diseases; treat reproductive tract infections in a timely manner and have sexual partners examined and treated if necessary; and treat pelvic inflammatory diseases in a timely and standardized manner to prevent sequelae. However, if ultrasound indicates pelvic fluid, if there is no discomfort, it is mostly physiological fluid and there is no need to panic. If combined with other discomfort, timely consultation should be made to clarify the diagnosis and treat inflammatory effusion as early as possible to avoid aggravation.