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Endometriosis is a condition in which endometrial, or endometrial like tissue grows outside of the uterus. Although in the vast majority of cases the endometriosis is located within the pelvis (on the uterosacral ligaments, in the ovaries or on the pelvic wall) it can rarely been found in other locations such as the lungs, umbilicus and skin.

In severe cases, large cystic lesions may form, and other lesions can invade the bladder or bowels and cause extensive adhesions.

It typically begins in adolescence with dysmenorrhoea, which gradually increases in severity over time (typically over a period of years). There is often a family history of endometriosis and possible hysterectomy + oophorectomy.

Example locations of endometriosis tissue

Example locations of endometriosis tissue

Epidemiology and Aetiology

  • Affects 5-10% of reproductive age women
    • About 1/3 of cases are asymptomatic
  • About 20% of patients will improve spontaneously
  • In the other 80% symptoms will be stable or gradually become more severe
  • Associated with reduced fertility
  • Risk factors include:
  • A genetic link has been established for endometriosis. The origin of the lesions is mostly retrograde menstruation; however for some of the further afield lesions, such as lungs, spread is thought to be through blood or lymph.
  • Some books mention Sampson‚Äôs theory, which ties in patient age, with their obstetric and gynaecological histories and predicts various things like the site of the lesions, and the likelihood they will recur after surgery. It‚Äôs quite complex, but likens the endometrial tissues to dandelion seeds spreading throuought the pelvis.
  • There are also some autoimmune and environmental factors implicated.

Endometriosis chocolate cyst


It is believed that retrograde flow of uterine contents Рup into the abdominal cavity rather than down into the vagina Рis important in the formation of endometriosis. This might explain why symptoms often start off mild shortly after menarche, and gradually progress Рtypically over a period of years.

  • It is thought that some anatomical variations – such as cervical stenosis, or other atypical variants of uterine anatomy can contribute to this process

It is also believed that there are genetic variations in cell apoptosis and adhesión al qualities, which mean that the tissue which has flowed in a retrograde fashion into the abdominal cavity is more likely to adhere to other structures, and then live on Рand continue to function as endometrial tissue.

  • There may also be important immunological factors relating to how the immune system deals with this tissue that allow it to survive in some individuals and go on to cause endometriosis

Symptoms typically settle during pregnancy and breastfeeding, but return again with the return of menstruation. Symptoms almost always settle with menopause.

The tissue outside of the uterus typically responds in exactly the same way as the uterine tissue – in response to hormonal changes with each menstrual cycle.

  • Endometriosis is a relapsing/remitting condition.
  • The endometrial tissue acts just like it would in the uterus, responding to cyclical hormone levels, growing and bleeding at certain times of the cycle.
  • If the tissue is in the ovaries, then chocolate cysts¬†may form into which the lesions bleed
  • Due to inflammation that happens at the site of the endometrial tissue, fibrosis occurs and in the abdomen and pelvis this leads to adhesions forming. These can lead to a frozen pelvis, and often affect fertility.
  • Very rarely these can be malignant

Some specialists divide endometriosis lesions into three types

  • Superficial endometrial implantation into the peritoneum
  • Endometrial lined ovarian cysts –¬†which may go on to form ‚Äėchocolate cysts‚Äô
  • Endometriotic nodules – large collections of endometrial, fat and connective tissue, found between the vagina and rectum


Signs and Symptoms

Many patients with endometriosis are asymptomatic. However endometriosis is a common cause of chronic pelvic pain, and can also cause deep dyspareunia, dysmenorrhoea and subfertility.

A typical presentation might include:

  • Dysmenorrhoea
    • Often from an early age
    • Generally progressive over time
    • Pain both pre-menstrual and menstrual – often beings a few days before menstruation and settles a few days afterwards
    • May be difficult to differentiate from primary dysmenorrhoea in teenage women
      • Primary dysmenorrhoea typically begins within 2 years of menarche, but usually does not worsen with time
  • Dyspareunia
  • Pain on vaginal examination / vaginal USS
  • Strong FHx of endometriosis and / or early hysterectomy
  • The rare but obvious sign is bleeding from odd places, and indeed depending on the site of the lesion patients may experience¬†haematuria, rectal bleeding, bleeding from the skin, or even in the eyes!
    • Bleeding from these other sites (if present) will usually be cyclical
  • If a chocolate cyst ruptures, then you get signs of an acute abdomen, acute pain, tenderness, fever etc.
  • All of the symptoms tend to be cyclical in response to circulating hormones; however some may persist for periods.

Abdominal Examination

  • Abdominal tenderness, without rebound or guarding
  • Usually no palpable masses

Pelvic examination (PV examination)

  • NOT appropriate¬†in an adolescent whom has never been sexually active
  • Indicated only if:
    • Not responding to conventional treatment, OR
    • Organic pathology is suspected
  • If indicated:
    • Speculum examination
    • Bimanual examination
      • Often painful
    • Consider STI testing if indicated

Differential Diagnosis

  • Primary dysmenorrhoea
  • Adenomyosis
  • Mittelschmirtz
  • PID / STI
  • IBS
  • Diverticulitis
  • Interstitial cystitis


The definitive ‚Äúinvestigation‚ÄĚ is the discovery of patches of endometriosis on laparoscopy – and in practice, in patients with severe and recurrent pain, this is often performed as the diagnostic test.

  • Therapeutic ablation can often be performed at the same time

Often, imaging is not able to detect areas of endometriosis within the abdomen.

Other investigations are often performed and may be supportive of the diagnosis, or of a differential.

  • Bloods for anaemia and hormone levels
    • CA-125 is often raised, but non-specific and should not be used as a diagnosis test
  • Urine dipstick to confirm haematuria
  • Laparoscopy, as diagnosis is made by actually seeing the lesions (plus or minus biopsy)
  • Transvaginal ultrasound to exclude other causes (endometrial cancers, ovarian cysts, adenomyosis)
    • Endometrotic lesions can sometimes be seen on USS
  • MRI scan may be able to detects endometriosis lesions, but its role in diagnosis is uncertain and not standard practice



  • If the endometriosis is asymptomatic then often no treatment is needed
  • Analgesia may help, but is not particularly effective
  • Suppression of ovarian function is effective at controlling pain. This can be achieved through hormonal means, or surgically
  • Start with non-surgical treatment options. If patients do not respond in 3-6 months – consider referral to gynaecology for consideration for surgical management

Medical management

  • Analgesia for the pelvic pain
    • Paracetamol 1g QID
    • NSAIDs – e.g. naproxen 750mg daily
    • Evidence for their effectiveness in endometriosis is por, but they are proven effective in other causes of dysmenorrhoea
  • Hormonal treatments
    • These aim to reduce or stop bleeding from endometrial tissue
    • COCP is typically the first-line treatment
    • MPA –¬†medroxyprogesterone acetate¬†is often considered a second line agent
      • Induces amenorrhoea
      • Side effects are common and can include:
        • Weight gain
        • Acne
        • Loss of libido
        • Moodiness
      • Not effective as a contraception – additional barrier contraception is recommended
    • Mirena / IUD also often considered as a second line option
      • Is effective and preventing retrograde uterine flow, but less effective at treating established endometriosis
    • Depot injection of MPA
      • Causes amenorrhoea in 50-70% of patients
    • Gonadotropin releasing hormone (GnRH) may also be used

Surgical management

Surgical treatment can involve several procedures

  • Incision or ablation of the pelvic adhesions
    • Typically should be performed by a gynaecologist with a special interest in this area
    • Is effective for pain relief, but 10-50% of patients have recurrence within1 2 months
    • Use of IUD or COCP for 18-24 months after surgery may prolong the effectiveness of surgery
  • Last resort ‚Äď Total hysterectomy and bilateral salpingo-oophorectomy. (Can be done vaginally, abdominally or laprascopically)
    • Patients with severe disease maybe advised early in the course of their illness to consider early family planning and subsequent hysterectomy and salpingo-oophorectomy
  • Fertility help for if the woman wishes to conceive


  • 30-50% of women with endometriosis have infertility
  • Early referral to gynaecology is the best way to maximise treatment effectiveness and fertility

Useful Resources

Two good websites to have a quick look at. They both have good explanations if revising for explaining stations for OSCEs!



  • Murtagh‚Äôs General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
  • Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
  • Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy

Read more about our sources

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