This disease process is also known as Endometriosis of the ovaries. Tiny implants of cells that line the uterine cavity become transplanted and form small cysts on the outside of the ovary. These cysts enlarge and produce Endometriosis of the ovary. They respond to hormone stimulation during the menstrual cycle and produce many small cysts, which may then occupy and even replace the normal ovarian tissue.

These endometriomas are filled with a thick chocolate-type material, which is the reason they are known as “chocolate cysts”. When this type of ovarian cyst ruptures, the material spills over into the pelvis and onto the surface of the uterus, bladder and bowel and the corresponding spaces between. Adhesions can develop because of this rupture and may lead to pelvic pain.