Medical Health Encyclopedia

Implants can form in many areas, most commonly in the following:

• The peritoneum. This is the smooth surface lining that covers the entire wall of the abdomen and folds over inner organs in the pelvic area.
• On or next to the ovaries.

Less commonly they occur in other areas:

• The cul-de-sac, an area between the uterus and rectum.
• The connective tissue that supports the uterus (called the uterosacral ligaments).
• The vagina.
• Fallopian tube.
• In the urinary tract (in about 20% of cases, usually without causing symptoms).
• In the gastrointestinal tract (in between 12% and 37% of patients).

Click the icon to see an image of the female reproductive anatomy.

Very rarely, they have been reported in areas far from the pelvis, including the lungs and even the arms and thighs.

Process of Endometriosis

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The process of endometriosis mimics menstruation at certain stages:

• Each month, the exiled endometrial implants respond to the monthly cycle just as they would in the uterus: they fill with blood, thicken, break down and bleed.
• Products of the endometrial process cannot be shed through the vagina as menstrual blood and debris does. Instead, the implants develop into collections of blood that form cysts, spots, or patches.
• Lesions may grow or reseed as the cycle continues.

The lesions are not cancerous, but they can develop to the point that they cause obstruction or adhesions (web-like scar tissue) that attach to nearby organs, causing pain, inflammation, and sometimes infertility.