What effect does endometriosis have on the organs that uterine cells (unnaturally) contact with?

Scarring sometimes: Endometriosis can cause scar tissue formation. The endometrial cells get implanted outside of the uterus with this problem. This is what leads to the painful periods. Most can be controlled with medications but sometimes surgical resection is needed

Endometriosis: The uterine cells in the unnatural sites will shed blood just like the natural menstruation. The accumulated blood in the unnatural sites forms hemorrhagic cysts of growing size as well as adhesion, thus causing the clinical symptoms of pain, reduced fertility, etc.