This is where fragments of the lining of the uterus (the endometrium) are found in other parts of the body. Up to 2 in 5 affected women become infertile as a result. The cause is unknown, though it is thought that in some cases it is due to the body not expelling the fragments properly during menstruation, and instead they travel through the fallopian tube and enter the pelvic cavity. Here, they grow on any organ and continue to respond to hormones created during menstruation, continuing to bleed each month.
For some women, there are no symptoms, however some will experience abnormally heavy periods accompanied by abdominal or lower back pains. Other symptoms may include pain during intercourse, diarrhoea and constipation.
The internal bleeding also causes pain, which is followed by a process of healing, the end result being internal scars.
Treatment may be given through the use of menstruation preventing drugs. Laser treatment or electric current treatment may be given to expel the remaining fragments. Pregnancy often relieves the condition significantly.