Endometriosis is a common condition where tissue that behaves like the lining of the womb (endometrium) is found in other parts of the body.
It can appear in many different places, including the ovaries, fallopian tubes, inside the tummy, and in or around the bladder or bowel.
Endometriosis mainly affects girls and women of childbearing age. It’s less common in women who’ve been through the menopause.