• Endometriosis is a common, recurring disease in women of reproductive age that may even persist into early menopause (1).
• Heterotopic islands of endometrial glands and stroma found outside the uterus:
  • Pelvic sites: Peritoneal surfaces (bladder, cul-de-sac, pelvic walls, ligaments, and fallopian tubes), vagina, cervix, lymph nodes, ovaries, bowel
  • Distant sites: Abdominal wall, spleen, gallbladder, stomach, nasal mucosa, spinal canal, lungs, breasts, diaphragm, pleura, pericardium
• Classified as peritoneal, ovarian, or deep endometriosis
• Staged according to the American Society for Reproductive Medicine surgical scoring system:
  • Based on disease severity: Extent and characteristics of endometrial implants and adhesions
  • Stage I (minimal) to IV (severe)
• System(s) affected: Reproductive
• Synonym(s): Endometriosis externa

ALERT
Staging is useful in therapeutic planning but does not correlate with severity of pain or predict response to treatment for symptoms or infertility.

Incidence

• Affects 0.5–5% of fertile women
• Found in 30–50% of infertile women (2)
• Found in 50–60% of women and adolescent women with pelvic pain (3)

ALERT
Pediatric Considerations
Endometriosis may begin with puberty, causing debilitating pelvic pain and severe dysmenorrhea associated with missed school, social, and family activities.

Pregnancy Considerations
Pelvic endometriosis generally is ameliorated with pregnancy, but infertility is significantly associated with the disease itself.

Geriatric Considerations
Although menopause often results in a resolution of symptoms, pelvic endometriosis may extend into menopause and is exacerbated by hormone replacement therapy (HRT).

Prevalence

• Predominant sex: Female only
• Affects 6–10% of reproductive-age women

• Diethylstilbestrol exposure in utero
• Low birth weight
• Obstruction of menstrual flow (Müllerian anomalies)
• Prolonged exposure to endogenous estrogen:
  • Early menarche
  • Short menstrual cycles
  • Late menopause
  • Delayed childbearing
  • Obesity
• Hereditary/genetic predisposition
• Exposure to endocrine-disrupting chemicals
• Increased dietary intake of red meat and trans fats

Genetics Genetic predisposition is common.

• Prevention is not possible, but some factors are considered protective:
  • Fruits, green vegetables, n-3 long-chain fatty acids
  • Multiple pregnancies
  • Prolonged lactation
• Early diagnosis and treatment might help prevent the possible sequelae.

• Not fully understood; tendency for abnormal endometrial tissue to implant and proliferate, causing chronic peritoneal inflammation
• Endometrial-associated infertility is multifactorial:
  • Pelvic inflammation
  • Anatomic disruption of pelvic structures (involvement of the fallopian tube may cause isthmic tubal obstruction)
  • Proliferation and activation of peritoneal macrophages (may predispose to gamete phagocytosis)
  • Alteration in eutopic endometrium

Not fully understood; theories include:

• Sampson theory: Retrograde menstruation results in peritoneal implantation and disease:
  • Affected women have an immune dysfunction that prevents clearing of implants
• Halban theory: Distant disease probably caused by hematogenous/lymphatic dissemination or metaplastic transformation
• Coelomic metaplasia: Coelomic epithelium undergoes metaplasia, forming functioning endometrium

Associated with increased risk of other autoimmune diseases (3); increased risk of ovarian, endometrioid, and clear-cell cancers as well as other cancers (e.g., non-Hodgkin lymphoma)