• The presence of normal endometrial mucosa (glands and stroma) abnormally implanted in locations other than the uterine cavity.


The exact causes of endometriosis is unknown in most cases.  Theories include conversion of similar cells (metaplasia) in response to hormones (e.g. coelomic epithelium); spread of normal endometrium via blood/lymphatic vessels; immunological dysfunction and retrograde menstruation (seems to be a fairly common phenomenon).  Although none of these have been proven, there are several known risk factors:

  • Family history
  • Early age of menarche; heavy periods; long duration of mentrual flow (this may be a proportional measure e.g. in short cycles)


  • Ectopic endometrium still contain hormone receptors that uterine endometrium does, and thus responds in a similar way too:
    • Growth in response to Progesterone and oestrogen; shedding/bleeding at menstruation
    • This process forms ‘chocolate cysts’ in the tissue affected (a combination of clotted blood and inflammation)
    • Long-term inflammation can cause the formation of pelvic adhesions, fibrosis and scarring.
      • This can affect fertility
  • The most common site of endometriosis is on the uterosacral ligment- although other common places include the ovaries/pelvic wall/pouch of Douglas.  Rarely, lesions can be found in the lungs/gi tract.


Around 1/3 of patients will be asymptomatic.  The most common symptoms are:

  • Dysmenorrhea (painful periods)
  • Heavy/irregular periods
  • Deep pelvic pain (may indicate pelvic adhesion)
  • Dyspareunia (usually deep)
  • Haematuria
  • Abruption of a chocalate cyst may cause features of an acute abdomen e.g. abdominal rigidity/guarding/tenderness, septic shock etc


  • Blood tests- Check for anaemia and hormone profile
  • Urinalysis and urine culture- confirm haematuria but also help differentiate cause from UTI/STD
    • NB if uncertain, these patient’s should be tested for STDs, but in general the history should suggest one or the other
  • Laporoscopy is the gold-standard investigation- exploratory procedure to look for signs of endometriosis:
    • black/blue or dark red ‘powder spots’ of endometrium can be seen against the paler pelvic tissues
    • There may be fistulae
    • There may also be clotted blood/bleeding
    • +/- biopsy to confirm.
  • Imaging (transvaginal USS, abdominal USS and MRI to exclude malignancy/cystic disease is important too


  • If asymptomatic- do nothing
  • If mildly symptomatic- analgesia may all that be required (NSAIDs preferred)
  • Active treatment for moderate-very severe disease includes
    • the oral contraceptive pill (combined or progestogen only)- first line for most patients
    • IUCDs
    • GnRH analogues e.g. Goserelin (should be prescribed with hormonal ‘add-back’ therapy to protect against potential side effects e.g bone loss)
    • Surgery
      • Diathermy (laser/bipolar) and dissection of adhesions are more routinely done compared to
      • Hysterectomy and salpingo-oophrectomy.
  • Management of fertility (e.g. infertility treatment may need to be considered at diagnosis and prior to any surgery)

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