The first specific guidance on endometriosis was published by NICE in 2017 and aims to raise awareness of the symptoms of endometriosis, and to provide clear advice on what action to take when women with signs and symptoms first present in healthcare settings. It also provides advice on the range of treatments available.

Endometriosis is a common, and potentially debilitating disease. It is thought to affect approximately 6-10% of the population, although prevalence rates may be much higher since a significant proportion of patients are asymptomatic.It is defined as the presence of endometrial-like tissue outside of the uterus, which can result in local inflammatory reactions, the formation of scar tissue and adhesions.2

Initial assessment and investigation of endometriosis

According to NICE, the most important factor in assessing endometriosis is to consider the diagnosis in the first place. Diagnosis can take up to 10 years from first presentation of symptoms, partly due to the ‘normalisation’ of pelvic pain by patients and partly due to falsely reassuring initial investigations.3 This delay in diagnosis has been reported to result in increased personal suffering, prolonged ill health and a disease state that is more difficult to treat.4

Given that up to half of all patients presenting with chronic pelvic pain potentially have an underlying diagnosis of endometriosis, having a high level of suspicion is important in making the diagnosis.3

Taking a full history with particular regard to key symptoms of endometriosis is vital. A pain diary can be helpful in highlighting a cyclical element to the pain, and this may be a useful initial tool when assessing a patient. An abdominal examination should be carried out on all patients to exclude an abdominal mass. Where appropriate, a pelvic examination should be performed in order to identify abdominal masses and pelvic signs, such as reduced organ mobility and enlargement, tender nodularity in the posterior vaginal fornix, and visible vaginal endometriotic lesions.4

Investigations for endometriosis

NICE guidance state that transvaginal and transabdominal ultrasound scanning should be considered as the first line investigation in patients with symptoms of endometriosis, with or without pelvic signs on examination.4

Ultrasound scans are able to identify endometrial deposits measuring 1cm or more in the ovaries, bowel, bladder or ureter, as well as adhesions and free fluid.5 Pelvic MRI imaging may have a role in the diagnosis of endometriosis, but should not be used first line. Current NICE guidance advocates the use of MRI to assess the extent of deep endometriosis involving bowel, bladder or ureter.

Referral to secondary care is usually indicated if patients are suffering with severe, persistent or recurrent symptoms where initial medical managements have been ineffective or not tolerated.

Pharmacological treatment

Treatment should be based on a woman’s symptoms rather than grade of endometriosis, and simple pain relief should be offered in the first instance. This should initially be in the form of paracetamol and anti-inflammatories, either alone or in combination. A three-month trial of analgesics is appropriate before considering alternative pharmacological treatments. If these simple measures fail to improve symptoms, neuromodulators (such as amitriptyline, duloxetine, gabapentin or pregabalin) may be considered.4

Combined oral contraceptives (COC) have been long used to help control symptoms of endometriosis, and their continued use is supported by NICE.

Historically, it was noted that the clinical symptoms of endometriosis improved during pregnancy, and this lead to the utilisation of oral contraceptives to mimic this state. By inhibiting the production of gonadal oestrogen and suppressing ovarian activity, there is a reduction in prostaglandin release resulting in decreased local inflammation.6 There is good evidence that the COC reduces dysmenorrhoea, dyspaerunia and chronic pelvic pain in patients with endometriosis.7

Some specialists advocate using low oestrogen COCs, with only a 4-day pill-free break rather than the usual 7-day break or, indeed, continuous administration of COCs. It would appear that these regimens result in a more even suppression of endometrial growth and is associated with better pain control. However, these benefits may be offset by the fast recovery of disease after ceasing treatment and the increased risk of thromboembolic events in higher risk patients.6

Progestogens, in its many forms, have been used in the treatment of endometriosis for the past 30 years and there is robust evidence that they are effective in reducing pain secondary to endometriosis. The mechanism of action is primarily due to reduced endometrial proliferation and the creation of an atrophic endometrium and a so-called ‘pseudopregnancy’ state. In a similar way to COCs, they also appear to reduce local inflammation which gives rise to endometrial deposits. They can be given orally, via depot, implant or via a levonorgestrel-releasing intrauterine system.

Other progestogens, including medroxyprogesterone acetate, norethisterone, cyproterone acetate, or dienogest, may also be used to treat pain associated with endometriosis. However, current advice does not support the use of danazol or gestrinone due to their severe anti-androgenic side effects.7,8

Gonadotrophin releasing hormone (GnRH) agonists suppress ovarian activity and induce a hypo-oestrogenic state, which has a beneficial effect on endometriosis symptoms. However, this ‘pseudomenopausal’ state can precipitate vasomotor symptoms as well as irreversible bone demineralisation. So-called ‘add back’ treatment is usually recommended in the form of low dose oestrogen and progesterone HRT to counteract these negative side effects.8

On balance, there is no evidence to suggest that one form of hormonal treatment is more effective than another in treating the symptoms of endometriosis. In practice the clinical decision to use one drug over another is dictated by the risk profile of the patient, side effect tolerability and patient personal preference.7

Newer treatments are on the horizon, but have not been endorsed in the recent NICE guidance. Aromatase inhibitors prevent the conversion of testosterone to oestrogen and have been shown to effectively reduce endometriosis-related pain.8 Selective oestrogen and progesterone receptor modulators, as well as immunotherapies, are also being explored with the potential to alter current established treatments regimens in the future.8

The recent NICE guidance states that there is currently no evidence to support the use of traditional Chinese medicine for the treatment of endometriosis.


  1. Giudice LC, Kao LC. Lancet. 2004;364(9447):789–799
  2. Kennedy S, Bergqvist A, Chapron C, D’Hooghe T, Dunselman G, Saridogan E, et al. Hum Reprod. 2005;20(10):2698–2704
  3. Pugsley Z, Ballard K. The British Journal of General Practice. 2007;57(539):470-476.
  4. Endometriosis: diagnosis and management NICE guideline [NG73] Published date: September 2017
  5. Holland, Cutner, Saridogan et al. BMC Women’s Health. October 2013. 13:43
  6. Zito G, Luppi S, Giolo E, et al. BioMed Research International. 2014;
  7. Guideline on the management of women with endometriosis. European society of human reporoduction and embryology. Issued : 18 September 2013
  8. Hickey et al. BMJ 2014; 348