Pelvic fluid that is 20mm is clinically likely to be a physiological fluid, often occurring in the second half of the menstrual period mainly due to follicular fluid, or lubricating fluid from the intestines. It often has no symptoms and does not cause pain in the lower abdomen, so it does not need to be treated. If the pelvic fluid is 20mm, accompanied by repeated pain in the lower abdomen, it is often due to exudation caused by inflammation of the pelvic cavity. In this case, anti-inflammatory treatment should be actively given, and you can take oral metronidazole tablets for 7 days, 3 times a day, 1 tablet a time. Since metronidazole may cause gastrointestinal reactions, it must be taken after meals. If you are allergic to metronidazole, it is recommended that you can switch to Chinese medicine for treatment, such as vajra vine capsule or gynecological rehabilitation capsule, both of which can effectively treat pelvic effusion, and it is also recommended to do physical therapy, which can improve local metabolism and promote the absorption of inflammation through thermal circulation.