1, planting theory. Menstrual reflux, endometrial implantation. During the menstrual period, menstrual blood is discharged downstream from the cervix and vagina, but a small amount of menstrual blood or endometrial debris falling off for other reasons is mixed together, flows into the abdominal cavity from the fallopian tube, and is planted on the surface of pelvic organs, forming endometriosis lesions.
2. Metaplastic intima. Serous epithelium, metaplastic intima. During the development of human embryo, the epithelial surfaces of ovary, peritoneum, vagina, rectum, diaphragm and navel are all metaplasia from body cavity epithelium. These tissues can be transformed into another tissue or metaplasia into endometrium under the stimulation of gonadal hormones, inflammation and mechanical factors.
3. Benign metastasis. Hemolymph, benign metastasis. This is a rare cause. Endometriosis, which often occurs in the lung, meninges, pericardium, limbs and other distal parts, is caused by the transfer of endometrial debris to an organ or tissue through blood circulation or lymphatic system.
4. Iatrogenic intimal transplantation. This is a kind of operation to transplant endometrium to some parts manually, which is more common in cesarean section, curettage in early and middle pregnancy, lateral perineal incision during delivery and induced abortion.