Why does endometriosis cause dysmenorrhea?

Endometriosis is a common gynecological disease. That is, when endometrial tissue with growth function appears in other parts besides the mucosa of the uterine cavity, it is called endometriosis. Although the endometrium can grow in other parts away from the uterus, most of them appear in the peritoneal surface of the reproductive organs and adjacent organs in the pelvic cavity, so it is often clinically called pelvic endometriosis.

If the endometrium grows in the myometrium, it is clinically called adenomyosis. Adenomyosis and endometriosis can exist at the same time, but most of them exist alone, mostly occurring in women aged 20 to 40.

The typical clinical manifestation of this disease is that the abdominal pain is most severe from 1 to 2 days before menstruation to the first day of menstruation, and then gradually alleviates and lasts until the end of menstruation. The pain is progressive and can radiate to the vagina, anus, vulva, buttocks and inner thighs. Some patients have anal swelling and pain. Severe pain may be accompanied by nausea, vomiting, diarrhea and other symptoms.

The cause of endometriosis is still unclear. Some people have observed that pregnancy or the use of sex hormones to suppress ovarian function can temporarily prevent the development of the disease, so it is believed that the onset of endometriosis is related to the cyclical changes of the ovaries. In addition, epidemiological surveys have also found that women with direct relatives suffering from the disease have a significantly increased chance of developing the disease, suggesting that the disease is related to genetics and may be a polygenic inheritance.

Endometriosis is caused by the growth of endometrial tissue in other parts of the body besides the uterine cavity mucosa. Generally, the lesions grow in the ovaries. 80% of patients have lesions involving one ovary, and about 20% have both ovaries affected at the same time. Other lesions are mostly in the pelvic peritoneum, recto-vaginal septum, etc. Since the ectopic endometrial tissue includes endometrial glands and stroma, it is also affected by ovarian hormones and can undergo cyclical changes such as proliferation, secretion, and bleeding. Since the ectopic endometrial bleeding cannot be drained and stimulates the surrounding tissues, it can cause uterine contraction and lead to dysmenorrhea.

The degree of pain caused by dysmenorrhea due to endometriosis is not necessarily proportional to the size of the lesion. For example, a larger ovarian endometriotic cyst may cause less pain, while small nodular lesions scattered on the pelvic peritoneum may cause severe pain.