B9. Endometriosis; pathophysiology, classification, symptoms and diagnosis

Page created on June 6, 2021. Last updated on January 17, 2022 at 12:55

Definition and epidemiology

Endometriosis is a condition characterised by ectopic growth of endometrial tissue outside the uterine cavity. It is unknown why endometrial tissue grows outside the uterine cavity, and how the cells can survive and proliferate there.

It’s a progressive disease, as the morphology of the extrauterine endometrial tissue changes over time.

It’s a common disease, affecting around 6 – 8% of women of reproductive age. It’s a common cause of infertility.


Some risk factors for endometriosis are known, most of which are associated with an increased oestrogen exposure:

  • Shorter menstrual cycles
  • Nulliparity
  • Early menarche
  • Late menopause
  • Obstruction to menstrual outflow (due to congenital abnormalities)
  • Family history
  • Low BMI


It is hypothesised that retrograde menstruation can spread viable endometrial cells to other organs, or that they may spread by haematogenic or lymphogenic pathways. It is also hypothesised that endometriosis develops from pluripotent coelomic cells.


We can distinguish four histopathological types of endometriosis:

  • Peritoneal endometriosis
  • Ovarian endometriosis
  • Adenomyosis
  • Deep infiltrative endometriosis (DIE)

Adenomyosis refers to the presence of endometrial tissue in the myometrium. It’s also known as endometriosis interna.

Deep infiltrative endometriosis refers to the presence of ectopic endometrium which infiltrates the peritoneum deeper than 5 mm. This is most commonly found in the rectovaginal septum, but it can be in any organ. DIE is also associated with hydronephrosis. This is the most severe type, but thankfully rare.

We can also distinguish into three morphological types based on location affected:

  • Endometriosis genitalis interna – uterus and fallopian tubes are affected
  • Endometriosis genitalis externa – other organs of the minor pelvis are affected
  • Endometriosis extragenitalis – outside the minor pelvis

Clinical features

The characteristic feature is dysmenorrhoea, pain during menstruation. However, as the disease progresses the pain can be continuous and always present.

Other symptoms include:

  • Menorrhagia
  • Dyspareunia
  • Dyschezia (pain on defecation)
  • Dysuria
  • Infertility

Patients may also have organ-specific symptoms depending on the location of the endometriosis.

The visual extension of the disease does not correspond with the pain intensity, but the depth of invasion does.

Diagnosis and evaluation

As always, a thorough medical history is necessary, as is a gynaecological examination. Nodules in the posterior fornix, adnexal masses, and immobility of the cervix or uterus may be present.

Imaging like ultrasound and MRi should be used before surgery, so that the location of the lesions is known beforehand. Renal ultrasound must always be performed to exclude hydronephrosis.

Imaging may reveal so-called chocolate cysts (endometrioma) of the ovary. These cysts contain degenerated menstrual blood which gives it a chocolate-like content.

Unfortunately, endometriosis is a histological diagnosis, and to diagnose it laparoscopy with biopsy of macroscopically suspicious lesions is required. There are no non-invasive methods to diagnose endometriosis. Laparoscopy may be used to diagnose and treat in the same procedure.

Physical examination, typical clinical features, and imaging may allow a presumed diagnosis of endometriosis. In this case, treatment can be initiated. If treatment is effective, the diagnosis of endometriosis is likely. If treatment is ineffective, laparoscopy should be performed to confirm or rule out the diagnosis.

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