Etiology

Age of onset: 20–40 years

Incidence: 2–10% of all women

Ethnicity: In the US, endometriosis is more common in white and Asian women than in black and Hispanic women.

The etiology of endometriosis is not yet fully understood; however, retrograde menstruation seems to play a major role in the pathogenesis of endometriosis.

Coelomic metaplasia

Iatrogenic implantation

Hematogenic and lymphogenic dissemination of endometrial cells

Hereditary component

Nulliparity

Prolonged exposure to endogenous estrogen (early menarche, late menopause)

Short menstrual cycles (< 27 days)

Menorrhagia (> 1 week)

Family history

In endometriosis, endometrial tissue occurs outside of the uterus.

Common locations of endometriotic implants include:

• Pelvic organs

  • Ovaries: most common site; often affected bilaterally

  • Rectouterine pouch

  • Fallopian tubes

  • Bladder

  • Cervix

• Peritoneum

• Extrapelvic organs (e.g., lung or diaphragm): less commonly affected

Regardless of where the endometrial tissue is located, it reacts to the hormone cycle in much the same way as the endometrium and proliferates under the influence of estrogen.

Endometriotic implants result in:

• ↑ Production of inflammatory and pain mediators

• Anatomical changes (e.g., pelvic adhesions) → infertility

• Nerve dysfunction