Pelvic effusion 27mm is mostly caused by chronic pelvic inflammatory disease, often accompanied by recurrent lower abdominal pain, fatigue, mental depression and other corresponding symptoms, and gynecological examination will reveal significant pressure pain in the uterine adnexa, which can be treated with anti-inflammatory treatment, which is a common gynecological inflammatory disease and is not serious. In addition, it is also necessary to take into account the clinical history. If there is a history of menopause and there is pain in the lower abdomen, bleeding due to rupture caused by ectopic pregnancy should be excluded. If lower abdominal pain occurs in the second half of menstruation, it is also recommended to exclude pelvic fluid caused by rupture of corpus luteum, and if necessary, posterior fornix aspiration is needed to determine whether the fluid is exudate or leaky, and then give treatment.