Endometriosis — Causes, Symptoms, Diagnosis & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Endometriosis is a chronic inflammatory condition in which endometrial-like tissue (glands and stroma similar to the uterine lining) grows outside the uterus. Common locations include the ovaries (endometriomas — 'chocolate cysts' containing old haemorrhagic fluid), fallopian tubes, peritoneum, uterosacral ligaments, rectovaginal septum, and bladder — and rarely, distant sites (bowel, diaphragm, lung). Endometriotic deposits respond to cyclical hormonal changes (oestrogen-driven proliferation and progesterone-driven decidualisation), causing bleeding, inflammation, and progressive scarring (adhesions, fibrosis) with each menstrual cycle. This accumulating inflammatory and fibrotic damage causes the characteristic symptoms: progressive dysmenorrhoea (menstrual pain) and chronic pelvic pain. Endometriosis is among the most common gynaecological conditions, yet is chronically underdiagnosed — the average time from symptom onset to diagnosis is 6-8 years, during which women often have their pain dismissed or attributed to normal menstruation.

The exact aetiology of endometriosis remains incompletely understood. Several mechanisms are proposed: Retrograde menstruation (Sampson's theory — most widely accepted): shed endometrial cells travel backwards through the fallopian tubes into the peritoneal cavity during menstruation; most women experience some retrograde menstruation, but in women with endometriosis these cells implant and proliferate — suggesting immune and hormonal dysregulation that prevents clearance. Coelomic metaplasia: peritoneal cells transform into endometrial-like tissue under hormonal stimulation. Lymphatic and vascular dissemination: explains rare distant implants (lung, brain). Stem cell seeding. Oestrogen dependence: endometriotic tissue produces its own oestrogen (from aromatase activity — even in low-oestrogen states), creating a self-sustaining oestrogenic microenvironment; relative progesterone resistance prevents normal decidualisation and shedding. Immune dysregulation: altered natural killer cell function and reduced peritoneal macrophage clearance of endometrial cells; elevated inflammatory cytokines (IL-6, IL-8, TNF-alpha) in peritoneal fluid. Risk factors: family history (first-degree relative increases risk 6-7 fold — strong genetic component with over 40 susceptibility loci identified); early menarche; short menstrual cycles (less than 27 days); heavy menstrual bleeding; mullerian anomalies (obstruction to menstrual outflow); low BMI; nulliparity. Protective factors: pregnancy (protective during gestation), prolonged breastfeeding, combined oral contraceptive use (suppresses ovulation and reduces retrograde menstruation).

The severity of symptoms correlates poorly with the extent of disease — a woman with minimal peritoneal deposits may have severe pain; a woman with large ovarian endometriomas may be asymptomatic. Core symptoms: Dysmenorrhoea (severe secondary dysmenorrhoea — menstrual pain significantly worse than 'normal' period cramps, often beginning 1-2 days before menstruation, progressive over years, not responding to simple analgesia like ibuprofen or paracetamol; typically described as 'crushing', 'stabbing', or 'like labour pains'). Deep dyspareunia (pain during or after deep sexual penetration — caused by endometriotic nodules in the uterosacral ligaments or pouch of Douglas; specifically worse in the second half of the cycle). Chronic pelvic pain: constant or cyclical non-menstrual pelvic pain. Cyclical bowel symptoms (deeply infiltrating endometriosis of the rectosigmoid — cyclical constipation, diarrhoea, rectal bleeding, tenesmus, or bloating coinciding with menstruation). Cyclical bladder symptoms (endometriosis on the bladder or ureter — cyclical dysuria, haematuria, or ureteric obstruction). Subfertility and infertility (pelvic adhesions distorting tubal anatomy; ovarian endometriomas impairing folliculogenesis; toxic peritoneal environment impeding fertilisation and embryo development). Fatigue (severe, often underappreciated — likely from chronic pain and inflammation). Symptoms often dismissed as 'just bad periods' — a significant barrier to timely diagnosis.

Clinical diagnosis: NICE (NG73, 2017) states that endometriosis should be considered in any woman (or girl) presenting with: chronic pelvic pain, severe dysmenorrhoea affecting daily activities, deep dyspareunia, cyclical bowel or bladder symptoms, infertility. Do not normalise menstrual pain — any woman whose period pain significantly impairs quality of life or is not controlled by over-the-counter analgesia and/or the combined pill warrants further assessment. Pelvic examination: may reveal uterosacral ligament tenderness, fixed retroverted uterus, adnexal masses (endometriomas), or tenderness in the pouch of Douglas — but a normal examination does not exclude endometriosis. Transvaginal ultrasound (TVUS): identifies ovarian endometriomas (chocolate cysts) and deeply infiltrating endometriosis of the rectosigmoid; soft markers for peritoneal endometriosis are being developed but TVUS cannot reliably detect all peritoneal deposits. MRI pelvis: superior for mapping deeply infiltrating endometriosis (rectovaginal, bladder, ureteric, diaphragmatic) pre-operatively; essential for surgical planning in complex disease. CA-125 blood test: not useful for diagnosis of endometriosis — elevated in moderate-severe disease but also in many other conditions (ovarian cancer, adenomyosis, fibroids, pelvic inflammatory disease); NICE does not recommend it for diagnosis. Definitive diagnosis: laparoscopy with direct visualisation of endometriotic deposits and histological confirmation (biopsy) — the gold standard. NICE NG73 states that a diagnosis can be made clinically and treatment initiated without confirmatory laparoscopy in women with typical symptoms; laparoscopy is indicated for diagnostic uncertainty or before surgical treatment.

Treatment aims to relieve symptoms, prevent progression, preserve fertility, and improve quality of life — there is no cure. Analgesia: NSAIDs (ibuprofen, naproxen — first-line for dysmenorrhoea; anti-prostaglandin effect; start 1-2 days before menstruation onset); paracetamol; opioids for severe breakthrough pain. Hormonal treatments (suppress oestrogen, induce pseudopregnancy or pseudomenopause, inhibit endometriotic tissue activity): combined oral contraceptive pill (COC — continuous (no pill-free interval) use is more effective than cyclic; suppresses ovulation and reduces retrograde menstruation; first-line for endometriosis-related dysmenorrhoea and pain); progestogen-only pill (norethisterone, desogestrel — anti-oestrogenic effect on endometriotic tissue); levonorgestrel IUS (Mirena — reduces HMB and dysmenorrhoea; particularly useful if contraception also needed); progestogen implant or injectable depot (medroxyprogesterone acetate depot — Depo-Provera); GnRH analogues (leuprorelin, goserelin, nafarelin — induce temporary medical menopause with amenorrhoea; most effective hormonal treatment for pain; significant bone loss with prolonged use — requires add-back oestrogen/progestogen (tibolone, norethisterone + oestradiol) if used more than 6 months; typically used pre-operatively to shrink disease or when surgery is deferred); GnRH antagonists (elagolix, linzagolix — oral daily tablets; faster onset than analogues; NICE TA773 approved linzagolix for moderate-severe endometriosis 2022); dienogest (progestogen — licensed specifically for endometriosis in several European countries and in Asia, not yet fully approved in UK). Surgical treatment: laparoscopic excision of endometriotic deposits (preferred over ablation in evidence base — removes disease completely; performed at BSGE-accredited specialist endometriosis centres for complex disease); laparoscopic drainage and cystectomy for endometriomas (improved fertility over drainage alone); excision of deeply infiltrating endometriosis (rectovaginal, bladder — requires specialist multidisciplinary team including colorectal surgeon if bowel involved). Hysterectomy + bilateral salpingo-oophorectomy (BSO): considered definitive treatment for women who have completed their family and have severe refractory disease — BSO removes the primary oestrogen source; HRT is given post-BSO in women below 51 to prevent osteoporosis and cardiovascular risk (endogenous oestrogen from external HRT is much lower than normal ovarian production and does not significantly stimulate residual endometriosis). IVF: for endometriosis-associated infertility — NICE recommends IVF after failed ovarian stimulation attempts; surgery before IVF improves ovarian reserve only if endometrioma is large (above 4 cm) — small endometriomas: observe.

Infertility (endometriosis accounts for 30-50% of female infertility cases — from tubal adhesions and scarring blocking egg transport, ovarian endometrioma reducing follicular reserve, and an inflammatory peritoneal environment hostile to sperm and embryo implantation; IVF is often required for severe disease). Endometrioma rupture (acute pelvic pain with haemoperitoneum — may mimic appendicitis; requires urgent laparoscopic surgery). Bowel obstruction from deeply infiltrating rectosigmoid endometriosis (partial or complete obstruction requiring specialist multidisciplinary colorectal surgery). Ureteric endometriosis (silent progressive hydronephrosis causing permanent renal damage if unrecognised — requires ureteric stenting and laparoscopic excision). Malignant transformation (ovarian endometrioma to endometriosis-associated ovarian cancer — rare, approximately 0.3-1% lifetime risk; most commonly clear cell and endometrioid histological types). Psychological complications: depression, anxiety, chronic fatigue, sexual dysfunction, and relationship difficulties from persistent pain affect the majority of women with moderate-to-severe disease.

No definitive prevention exists for endometriosis. Long-term use of the combined oral contraceptive pill (particularly continuous use without a pill-free interval) appears to reduce endometriosis risk and slow disease progression — and is the first-line treatment for young women with suspected or confirmed endometriosis who do not want to conceive immediately. Treat retrograde menstruation risk factors: address outflow obstruction abnormalities (vaginal or cervical stenosis) promptly. Regular follow-up with a gynaecologist is essential — endometriosis is a progressive condition requiring ongoing management; symptoms may wax and wane. Multidisciplinary care at BSGE-accredited endometriosis centres for women with severe or complex disease. Psychological support — endometriosis has a profound impact on mental health, relationships, and occupational functioning; access to psychosexual therapy, counselling, and peer support (Endometriosis UK) is important. During menopause, most women find endometriosis-related symptoms improve significantly as oestrogen levels fall; HRT after BSO uses the minimum dose effective for menopausal symptom control.

Consult your GP for: period pain that is severe enough to interfere with daily life, work, or school; pain that is not adequately controlled by over-the-counter analgesia (ibuprofen, naproxen); pain during sexual intercourse; cyclical bowel or bladder symptoms; unexplained subfertility or difficulty conceiving. Do not accept 'bad periods are normal' — severe dysmenorrhoea that impairs quality of life warrants investigation and treatment. NICE states GP should consider endometriosis at the first consultation for these symptoms and offer appropriate treatment or refer to gynaecology. Seek urgent gynaecological assessment for: sudden severe pelvic pain (possible endometrioma rupture — may mimic appendicitis), large pelvic mass on ultrasound, suspected obstruction of the bowel or ureter from endometriosis, or any concern about ovarian malignancy (endometriomas rarely transform — but monitoring is needed). Request referral to a BSGE-accredited endometriosis centre for: complex or deeply infiltrating endometriosis, surgery planned, recurrent disease after previous surgery, or disease involving bowel or urinary tract.