Endometriosis is a common condition in which endometrial tissue grows outside of the womb. Endometrial cells migrate from the inner lining of the uterus (see figure 1) and form benign implants in areas such as the fallopian tubes, ovaries, intestine and in some cases the heart and lungs. The method of cell migration is still unclear but some of the hypotheses are listed below:
- Retrograde menstruation (RM)- blood which carries endometrial cells flows back from the uterus into the fallopian tubes where they subsequently implant. Openings in the fallopian tubes allow the cells to spread to the bowels. However, RM is more common than endometriosis so there must be other factors involved if this is to be true.
- Dysfunction in the immune system- B and T cells don’t respond to endometrial implants allowing implants to grow.
- Metaplastic theory- Perimetrial cells ( from the perimetrium lining see figure 1) spontaneously transform into endothelial cells as they are from the same cell line. This would explain why patients who have hysterectomies can still contract endometriosis.
- Benign metastases- endometrial cells can travel through the blood and lymph to implant around the body. This would explain why implants are found in the heart and lungs.
Although the implants are benign they can affect a patient profoundly due to slight differences in the endometrial implant cells.
- Endometrial implant cells produce their own oestrogen causing hormone imbalances.
- Endometrial implant cells release pro-inflammatory factors causing chronic inflammation.
- They can form endometriomas on the ovaries which trap blood and tissue and are painful when they rupture.
- Endometrioma cells are prone to mutations in genes (PTEN and ARDIA) which increases the risk of ovarian cancer.
Treatment for the condition revolves around managing pain, limiting the progression of the implants and addressing the subfertility that may occur. Hormone treatments and surgery ( excision of implants or hysterctomies or oorecytomies are commonly used. This condition can cause physical and emotional distress to patients especially if they are considering having a child due to associated subfertility.
Of interest: Endometriosis can make a pregnancy more risky as women with the condition are 1.5 times more likely to have a preterm baby. Furthermore, Placenta Previa (a condition where the placenta attaches to the bottom of the uterus) is more prevalent in women with endometriosis. This condition increases the risk of a ruptured placenta during labour which can cause severe bleeding and a higher risk of preeclampsia.