Last updated: May 19, 2021

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Endometriosis is a common, benign, and chronic disease in women of reproductive age that is characterized by the occurrence of endometrial tissue outside the uterus. The etiology of endometriosis is not yet fully established; however, retrograde menstruation is one of several factors involved. Symptoms include dysmenorrhea, dyspareunia, chronic pelvic pain, and infertility. Treatment is based on the individual disease manifestation and may either involve the administration of pain relievers and hormonal therapy or surgical removal of endometriotic tissue. Endometriosis tends to recur, but symptoms and disease spread improve after pregnancy in many cases, as well as in menopause.

  • 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.

Epidemiological data refers to the US, unless otherwise specified.

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

Endometriosis may also be asymptomatic in many women and appear as an incidental finding during surgery performed for another reason.

Normally the severity of the findings does not correlate with the severity of symptoms.

Macroscopic findings

  • Endometrium: endometrial implants that present as yellow-brown (sometimes reddish-blue) blebs, islands, or pinpoint spots
  • Ovaries
    • Gunshot lesions or powder-burn lesions
      • Black, yellow-brown, or bluish nodules or cystic structures
      • Seen on the serosal surfaces of the ovaries and peritoneum
    • Ovarian endometriomas or chocolate cysts; : cyst-like structures that contain blood, fluid, and menstrual debris
  • Fallopian tubes: salpingitis isthmica nodosa
    • Nodular tube changes, resulting in:

Microscopic findings

For more information, see “Differential diagnosis of dysmenorrhea and menorrhagia.


The differential diagnoses listed here are not exhaustive.

We list the most important complications. The selection is not exhaustive.

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