Rectal fossa fluid is also known as pelvic fluid, pelvic fluid is a symptom found by ultrasound, and there are physiologic fluid and pathological fluid. Rectal fossa fluid 15mm is not serious, in many cases rectal fossa fluid is physiological fluid, in the ovulation period, before menstruation and pregnancy will have a small amount of rectal fossa fluid phenomenon, such as not accompanied by other uncomfortable symptoms do not need to be treated. Pathological rectal fossa effusion is often accompanied by symptoms, such as low back pain, lower abdominal pain, leukorrhea, etc., gynecological internal diagnosis of the uterus, adnexal pressure or palpable mass, most commonly found in pelvic inflammatory disease, ectopic pregnancy, luteal rupture, pelvic tumors and other diseases. Relevant laboratory tests can be carried out to take targeted treatment for the cause of the disease. Inflammatory diseases can be treated with anti-inflammatory drugs, such as cephalosporin antibiotics, etc., under the guidance of the doctor, and ectopic pregnancy, rupture of corpus luteum, and pelvic tumors can be treated with surgery if necessary.