Endometriosis

Endometriosis is a chronic, oestrogen-dependent inflammatory condition in which endometrial-like tissue lies outside the uterine cavity. It most commonly affects the ovaries, pelvic peritoneum, and uterosacral ligaments. It can affect virtually any pelvic or, less commonly, extrapelvic site.

It is common, affecting a significant proportion of women of reproductive age, but frequently underdiagnosed and diagnostically delayed.

The characteristic clinical triad is chronic pelvic pain, dysmenorrhoea, and deep dyspareunia. There is also a substantial association with infertility.

It warrants individualised, multidisciplinary management addressing both symptomatic relief and, where relevant, fertility.

Pathophysiology and classification

• The precise mechanism by which endometrial-like tissue becomes established at ectopic pelvic and extrapelvic sites remains incompletely understood.
• The most widely accepted theory is retrograde menstruation. Menstrual tissue passes retrogradely through the fallopian tubes into the pelvic cavity rather than being expelled by the normal, antegrade route.
• This is a plausible but incomplete explanation, because retrograde menstruation occurs commonly in women without endometriosis.
• Additional factors are likely to contribute to established, symptomatic disease. They include altered immune surveillance and clearance of ectopic tissue. Possible coelomic metaplasia or lymphatic and haematogenous spread may account for more distant lesions.
• Ectopic endometrial-like tissue responds to the cyclical hormonal fluctuations of the menstrual cycle like normal intrauterine endometrium. It proliferates and, when hormonal support withdraws at the end of the cycle, bleeds locally.
• This cyclical bleeding at the ectopic site produces local inflammation, fibrosis, and over time adhesion formation and structural distortion of pelvic anatomy, characteristic of more advanced disease.
• Endometrioma is a common pattern of ovarian involvement. It is an ovarian cyst filled with old, altered blood, giving the characteristic "chocolate cyst" appearance.
• Deep infiltrating endometriosis is disease penetrating more than five millimetres beneath the peritoneal surface. It is a more severe pattern. Where deep lesions affect adjacent bowel or bladder, they cause deep dyspareunia and bowel or bladder symptoms.

• The classic symptom triad is chronic pelvic pain, dysmenorrhoea, and deep dyspareunia.
• Pelvic pain is typically cyclical and related to menstruation, though it frequently becomes more constant and persistent as disease progresses.
• Dysmenorrhoea is severe and often progressively worsening.
• Deep dyspareunia is characteristically related to deep penetration and specific positions, reflecting frequent involvement of the posterior compartment and uterosacral ligaments.
• Where deep infiltrating disease affects the bowel or bladder, additional symptoms include cyclical bowel symptoms (including pain with defecation, dyschezia) and cyclical urinary symptoms.
• A substantial proportion of affected women have chronic fatigue and a broader impact on quality of life and function.
• Infertility is a common, significant association, affecting a substantial proportion of women with confirmed endometriosis.
• Proposed mechanisms include pelvic adhesion formation and distorted tubo-ovarian anatomy, an altered peritoneal and follicular fluid environment, and in some cases direct ovarian tissue damage from endometrioma formation.
• The extent of disease seen at laparoscopy correlates poorly with symptom severity. Some women have extensive disease with modest symptoms, while others have severe, disabling symptoms despite limited disease on direct visualisation.
• This matters for counselling and contributes to the diagnostic delay characteristic of the condition.
• Diagnostic delay is well documented and frequently extends many years from symptom onset to diagnosis.
• It reflects the frequent normalisation or dismissal of significant menstrual pain as an ordinary part of menstruation, and the limitations of non-invasive diagnostic approaches.
• Take reported menstrual pain seriously and maintain clinical suspicion where the symptom pattern is compatible with this diagnosis.

• Diagnostic laparoscopy, with direct visualisation and ideally histological confirmation of biopsied lesions, has historically been the diagnostic gold standard.
• Contemporary guidance increasingly supports a clinically-led diagnosis in many cases, because laparoscopy is invasive. A confident clinical diagnosis, supported by imaging where relevant, can guide initial management without surgical confirmation in every case.
• Pelvic ultrasound by an appropriately experienced practitioner can identify endometrioma and, with more specialised expertise, certain deep infiltrating lesions.
• Standard ultrasound has more limited sensitivity for superficial peritoneal disease. A normal ultrasound does not exclude the diagnosis where the clinical presentation is otherwise compatible.
• Magnetic resonance imaging has superior sensitivity for deep infiltrating disease. It gives detailed anatomical information for surgical planning where more extensive or complex disease is suspected. It similarly cannot reliably exclude superficial peritoneal disease.
• A structured clinical history of the characteristic symptom pattern, with careful pelvic examination, is the essential foundation of assessment.
• Examination may reveal tenderness, reduced uterine mobility, or palpable nodularity along the uterosacral ligaments. A normal examination does not exclude the diagnosis.
• Contemporary practice supports starting empirical medical treatment on a compatible clinical presentation. Reserve laparoscopy for diagnostic uncertainty, inadequate response to empirical treatment, or when surgical management is being specifically considered.

• Nonsteroidal anti-inflammatory drugs give symptomatic pain relief and are a reasonable part of initial management. They are generally insufficient as sole treatment of the underlying condition.
• Hormonal treatment suppresses the cyclical hormonal fluctuation that drives ectopic endometrial tissue activity. It is the mainstay of medical management.
• Effective, commonly used first-line options are combined hormonal contraception and progestogen-only treatment.
• Use combined hormonal contraception particularly as a continuous or extended cycle regimen to minimise the frequency of withdrawal bleeding.
• Progestogen-only options include the levonorgestrel-releasing intrauterine system, oral progestogens, or a progestogen-only implant.
• Gonadotropin-releasing hormone agonists or antagonists suppress ovarian oestrogen production more profoundly. They are effective second-line treatment for pain not controlled with standard first-line hormonal approaches.
• They generally need concurrent low-dose hormone replacement "add-back" therapy. This mitigates the menopausal-type adverse effects and bone density impact of profound suppression, which matters because treatment is frequently prolonged.
• Surgery, typically laparoscopic, comprises excision or ablation of visible endometriotic lesions, with adhesiolysis where relevant. It is an important option for pain not adequately controlled by medical management alone, or where fertility is a specific treatment goal.
• Individualise the surgical approach and extent to the pattern and severity of disease. Ideally, a specialist endometriosis surgical service delivers it for more complex, deep infiltrating disease.
• Manage endometriosis-related infertility with individualised, specialist fertility assessment and counselling.
• Surgical management of endometriosis improves natural fertility potential in some cases. Assisted reproductive technology, including in vitro fertilisation, is an additional option for appropriately selected women.
• Use multidisciplinary management. Pain management specialists help with chronic, persistent symptoms not fully responsive to standard hormonal and surgical treatment.
• Physiotherapy addresses associated pelvic floor dysfunction.
• Psychological support addresses the often profound impact of this chronic condition on quality of life, relationships, and fertility. The condition is common but frequently underrecognised and undertreated.