Endometriosis is an inflammatory disorder caused when endometrial cells from the uterus that are typically shed during menstruation migrate and thrive elsewhere in the body. It is a common condition in women, occurring with various degrees of severity in up to 10 percent of women of child bearing age. The endometrial cells can form cysts which can either press against other organs (most notably, the bladder). Endometrial cysts can also rupture and bleed, causing a medical emergency.