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:
- Coelomic metaplasia
- Iatrogenic implantation
- Hematogenic and lymphogenic dissemination of endometrial cells
- Hereditary component
Risk factors 
- 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:
- Ovaries: most common site; often affected bilaterally
- Rectouterine pouch
- Fallopian tubes
- Extrapelvic organs (e.g., lung or diaphragm): less commonly affected
- Pelvic organs
- 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
|Clinical features of endometriosis|
|Location of endometriotic lesions||Clinical features|
|Uterus (common)|| |
|Urinary tract || |
|Abdominal wall (rare)|| |
|Thorax (rare)|| |
Endometriosis is often asymptomatic and may be an incidental finding during surgery for other conditions.
- Patient history
- Physical examination
Transvaginal ultrasound (best initial test)
- The uterus is generally not enlarged.
- Evidence of ovarian cysts (chocolate cysts)
- Nodules in bladder or rectovaginal septum
- Laparoscopy (confirmatory test): may show endometriotic implants and adhesions
Normally the severity of the findings does not correlate with the severity of symptoms.
- Endometrium: endometrial implants that present as yellow-brown (sometimes reddish-blue) blebs, islands, or pinpoint spots
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
- Gunshot lesions or powder-burn lesions
- Fallopian tubes: salpingitis isthmica nodosa
- Normal endometrial glands
- Normal endometrial stroma
- Preponderance of hemosiderin laden macrophages due to cyclic hemorrhages into endometriomas
For more information, see “Differential diagnosis of dysmenorrhea and menorrhagia”.
- Definition: benign disease characterized by the occurrence of endometrial tissue within the myometrium due to hyperplasia of the endometrial basal layer
- Epidemiology: peak incidence at 35–50 years
Etiology: The exact etiology is unknown, though some risk factors have been identified:
- Uterine fibroids
- May be asymptomatic
- Abnormal uterine bleeding
- Chronic pelvic pain, aggravated during menses
- Globular, uniformly enlarged uterus that is soft but tender on palpation
Diagnosis is clinical and may be supported by transvaginal ultrasound and MRI findings
- Asymmetric myometrial wall thickening 
- Myometrial cysts
- Histology serves to confirm the diagnosis.
- Diagnosis is clinical and may be supported by transvaginal ultrasound and MRI findings
- Combined oral contraceptives ,
- Progestin-only contraception (e.g., IUD, continuous-use contraceptive pill)
- NSAIDs for pain relief
- GnRH agonists
- Hysterectomy is the definitive treatment.
- Excision of single, organized adenomyomas.
The differential diagnoses listed here are not exhaustive.
Asymptomatic endometriosis 
- Expectant management is sufficient for most patients.
- Mild to moderate pelvic pain without complications
- Severe symptoms: GnRH agonists (e.g., buserelin, goserelin) and estrogen-progestin OCPs
First-line: laparoscopic excision and ablation of endometrial implants
- To confirm the diagnosis and exclude malignancy (see “Diagnostics” above)
- To treat patients who do not respond to pharmacological therapy
- To treat expanding endometriomas and complications, including:
- Infertility (Laparoscopy significantly improves natural conception rates.) 
- Bowel and/or bladder obstruction
- Rupture of endometrioma
Second-line: open surgery with hysterectomy with or without bilateral salpingo-oophorectomy
- Treatment-resistant symptoms
- No desire to bear additional children
- Endometriosis in the uterotubal junction inhibits implantation of the zygote: ↑ risk of ectopic pregnancy 
Endometriosis → fibrous adhesions → strictures and entrapment of organs
- Intestines: constipation or diarrhea; in rare cases, intestinal obstruction, ileus, or intussusception may occur 
- Ureter: urine retention
- Endometriosis is associated with a slightly elevated risk of ovarian cancer. 
We list the most important complications. The selection is not exhaustive.