The adnexa generally refers to a woman’s fallopian tubes and ovaries. A low density shadow in the left adnexal region may be caused by follicles, ovarian cysts, tubal cysts or hydrosalpinx. If it is physiologic, it is usually not serious. If it is pathologic, it is usually more serious and requires early treatment. 1. Follicles: produced by the female ovaries, which can be shown as low-density shadows during imaging. This is a physiologic phenomenon and generally does not require treatment. 2. Left ovarian cysts: they can be divided into physiologic cysts and pathologic cysts. (1) Physiologic cysts: they usually do not harm health and tend to disappear on their own within 2-3 menstrual cycles. They are usually not serious. (2) Pathological cysts: cysts will not disappear on their own and will continue to grow in size, accompanied by pain in the left lower abdomen and menstrual abnormalities. If the treatment is not timely, the cyst may rupture and become infected, which is more serious. 3. Left fallopian tube cyst: it is caused by chronic inflammation and is mostly benign. If the left tubal cyst is small, there may be no obvious symptoms. If the left fallopian tube cyst is large, frequent urination, infertility and other problems can occur, this is more serious. 4. Hydrocele in the left fallopian tube: The watery fluid wrapped in the fallopian tube due to tubalitis, tubal pregnancy and other diseases will seriously affect the fertility of women of childbearing age, so this kind is more serious. Examination found that there is a low density shadow in the left adnexal area, you should go to the gynecology department of the hospital in time to find out the cause of the problem and then carry out standardized treatment under the guidance of the doctor.