Endometriosis — Symptoms, Causes & Treatment | MyMedicPlus

Endometriosis is a chronic, oestrogen-dependent inflammatory condition in which tissue histologically resembling the endometrium (uterine lining — glands and stroma) grows and persists at ectopic sites outside the uterus, most commonly on the pelvic peritoneum, ovaries (endometriomas — 'chocolate cysts'), fallopian tubes, uterosacral ligaments, rectovaginal septum, bladder, and bowel. It affects approximately 10% of women and girls of reproductive age globally — an estimated 190 million individuals worldwide — making it one of the most prevalent gynaecological conditions. Despite this high prevalence, the average delay between symptom onset and definitive diagnosis remains 7–10 years in most countries, largely due to normalisation of severe menstrual pain by patients and clinicians, lack of public awareness, and the requirement for laparoscopic confirmation. Endometriosis is classified by the revised American Society for Reproductive Medicine (rASRM) staging system into four stages (I–IV: minimal, mild, moderate, severe) based on the extent of peritoneal lesions, adhesions, and endometriomas; however, disease stage correlates poorly with symptom severity or fertility impact. Deep infiltrating endometriosis (DIE — lesions penetrating more than 5 mm below the peritoneal surface) causes the most severe pain and functional impairment. Endometriosis has no cure, but multidisciplinary management dramatically improves quality of life and preserves fertility.

The aetiology of endometriosis remains incompletely understood despite decades of research — multiple complementary mechanisms are implicated. Retrograde menstruation (Sampson's theory — 1927) remains the most widely accepted hypothesis: viable endometrial cells shed during menstruation travel retrogradely through the fallopian tubes into the peritoneal cavity, implant on pelvic surfaces, and establish ectopic lesions in susceptible women. However, retrograde menstruation occurs in 90% of women with patent tubes, while endometriosis develops in only 10%, suggesting that altered immune surveillance is essential for disease establishment. Coelomic metaplasia: transformation of mesothelial cells lining the peritoneum (derived from the embryonic coelomic epithelium, which also gives rise to the endometrium) into endometrial-like tissue. Lymphatic and vascular dissemination explains rare extra-pelvic disease (diaphragm, pleura, liver, brain). Stem cell seeding: bone marrow-derived endometrial progenitor cells contribute to ectopic lesions. Genetic predisposition: first-degree relatives of affected women have a 7-fold increased risk; genome-wide association studies (GWAS) have identified multiple risk loci including GREB1, WNT4, CDKN2BAS, and FN1. Inflammatory and immune factors: aberrant macrophage function, reduced NK cell activity, and pro-inflammatory cytokine milieu (IL-1, IL-6, IL-8, TNF-alpha) in the peritoneal fluid of women with endometriosis facilitate implantation and vascularisation. Oestrogen dependence: endometriotic lesions express high local aromatase activity, generating their own oestrogen supply and causing relative progesterone resistance.

Endometriosis causes a characteristic symptom triad of cyclical pelvic pain, infertility, and fatigue. Dysmenorrhea (painful periods): severe cramping pelvic pain starting 1–2 days before and worsening through menstruation — often described as 'worse than labour' by many patients; the key distinguishing feature from primary dysmenorrhea is the progressive worsening over years and failure to respond adequately to NSAIDs or the combined oral contraceptive pill. Chronic pelvic pain (non-cyclical): continuous or intermittent pelvic pain throughout the month, often with cyclical exacerbation; deep infiltrating endometriosis (DIE) causes severe, constant low pelvic pain from nerve infiltration. Dyspareunia (painful intercourse): particularly deep dyspareunia on uterine movement and in specific positions, from posterior pelvic endometriosis, uterosacral ligament involvement, and adhesions causing fixed retroverted uterus. Dyschezia (painful defaecation): cyclical pain on opening bowels, rectal bleeding, diarrhoea, or constipation during menstruation — indicating bowel endometriosis; sigmoidoscopy or rectal biopsy may be required. Bladder symptoms: cyclical haematuria, dysuria, and urinary urgency from bladder endometriosis (rare — 1–2%); requires cystoscopy. Infertility: 30–50% of women with endometriosis experience infertility — caused by anatomical distortion from adhesions, impaired egg-sperm transport, an altered peritoneal inflammatory environment hostile to fertilisation, and potential direct effects on egg quality. Approximately 25% of women with endometriosis are asymptomatic.

Transvaginal ultrasound (TVUS) is the first-line imaging investigation — highly sensitive (91%) and specific (97%) for detecting ovarian endometriomas; experienced operators can also detect deep infiltrating endometriosis in the posterior compartment, bladder, and bowel using the 'sliding sign' (posterior cul-de-sac mobility assessment). MRI pelvis provides detailed mapping of deep infiltrating endometriosis (posterior cul-de-sac, rectovaginal septum, bladder, ureter, and bowel) — essential for surgical planning in complex DIE cases; also detects adenomyosis (uterine involvement). Diagnostic biomarkers: serum CA-125 is elevated in moderate-to-severe endometriosis (sensitivity 50–60%, specificity 70–80% — insufficient for screening); no blood-based biomarker is currently clinically validated for diagnosis. Definitive diagnosis has historically required laparoscopic visualisation (with histological confirmation on biopsy) as the gold standard. However, current NICE guideline (NG73, 2017) and international guidance now support empirical medical treatment (hormonal therapy) in women with classical symptoms and normal or positive ultrasound findings without mandatory laparoscopic confirmation first — this approach reduces surgical delays and costs while managing symptoms. Laparoscopy remains essential when diagnosis is uncertain, medical treatment fails, or surgical staging and treatment are planned. Classification: rASRM staging I–IV at laparoscopy; ENZIAN classification for DIE (more reproducible).

Medical management — the mainstay for pain without immediate fertility intent: Combined oral contraceptive pill (COCP): first-line hormonal option — suppresses ovulation, reduces endometrial stimulation, and provides 60–70% pain relief; continuous use (tricycling or 365-day regimens without pill-free interval) is more effective than cyclic use for dysmenorrhea. Progestins: norethindrone acetate (5–10 mg/day), medroxyprogesterone acetate (150 mg IM every 3 months), dienogest (2 mg/day — specifically licensed for endometriosis, highly selective progestin with low androgenic and oestrogenic activity, minimal systemic side effects) — reduce endometriotic lesion activity by inducing decidualisation and atrophy. Levonorgestrel-releasing intrauterine system (LNG-IUS — Mirena): highly effective for dysmenorrhea and pelvic pain — local progestin with minimal systemic effects; suitable for women who cannot use combined hormonal contraception. GnRH agonists (leuprorelin, goserelin, nafarelin) plus hormonal add-back (low-dose oestrogen-progestogen): most potent medical suppression — inducing pseudo-menopause; reserved for moderate-to-severe disease; used for maximum 6 months per course without add-back (bone density concerns), or longer with add-back. GnRH antagonists (elagolix, relugolix): more rapid onset, dose-titratable, and reversible suppression; increasingly used for moderate-to-severe disease. Surgical management: laparoscopic excision (not ablation — recurrence rates are lower with excision) of superficial and deep endometriotic lesions; laparoscopic cystectomy for endometriomas above 4 cm (reduces recurrence versus aspiration); bowel resection and shaving for rectovaginal DIE; requires specialist endometriosis surgical team. Fertility management: laparoscopic excision of endometriosis improves spontaneous conception rates in stage I–II disease (Cochrane 2014); IVF is the treatment of choice for endometriosis-related infertility with tubal involvement or failed surgical treatment.

Infertility affects 30–50% of women with endometriosis — the most common reason patients seek specialist care; endometriosis is the primary diagnosis in 25–50% of couples undergoing fertility investigation. Mechanisms include mechanical distortion from pelvic adhesions causing tubal occlusion, altered peritoneal immune environment reducing sperm function and embryo implantation success, direct impairment of folliculogenesis and egg quality from endometrioma proximity to ovarian cortex, and progesterone resistance impairing endometrial receptivity. Ovarian endometrioma complications: 'chocolate cysts' can rupture spontaneously during menstruation, causing acute peritoneal irritation and severe pelvic pain requiring emergency laparoscopy; torsion of an endometrioma-containing ovary is a gynaecological emergency. Bowel obstruction from rectosigmoid endometriosis causes cyclical bloating, incomplete obstruction, and — rarely — complete obstruction requiring emergency bowel resection. Ureteral endometriosis causes silent progressive hydronephrosis and renal impairment in 0.1% — late diagnosis causes permanent renal damage. Sciatic nerve endometriosis causes cyclical sciatica (buttock, posterior thigh, and foot pain) and foot drop at menstruation. Psychological impact: chronic pain with diagnostic delay causes depression (30–50% of patients), anxiety, post-traumatic stress, and significant relationship and professional dysfunction; untreated psychological comorbidity worsens pain perception and treatment outcomes. Recurrence after surgery: even after expert surgical excision, lesion recurrence requiring reoperation occurs in 20–30% of patients at 5 years — underscoring the need for ongoing medical suppression after surgery.

See a GP or gynaecologist for: progressively worsening period pain that limits daily activities or requires strong painkillers, pain during or after sexual intercourse (deep dyspareunia), pelvic pain outside of periods, difficulty conceiving after 6-12 months of unprotected intercourse, or cyclical bladder or bowel symptoms (pain with urination or defaecation at menstruation). Do not accept a dismissal of severe menstrual pain as normal — endometriosis is a medical condition requiring investigation and treatment. Seek urgent assessment for: sudden severe pelvic pain (possible endometrioma rupture or ovarian torsion — surgical emergency), fever with pelvic pain (possible pelvic inflammatory disease), or acute urinary retention from pelvic mass. Women already diagnosed with endometriosis should seek reassessment if: their usual pain pattern changes significantly, new symptoms appear (rectal bleeding, haematuria at menstruation), or they are planning pregnancy — fertility-sparing surgical options and IVF timing require specialist guidance.

No proven primary prevention strategy exists for endometriosis, as the exact aetiology remains incompletely understood. The combined oral contraceptive pill reduces endometriosis progression risk in susceptible women by suppressing ovulation and reducing menstrual volume — continuous use (without pill-free week) is most effective. Early diagnosis is crucial — reducing the diagnostic delay from the current 7–10 year average to under 2 years would allow earlier hormonal suppression and potentially limit progressive disease advancement and organ damage. Women and girls should be empowered to seek medical assessment for severe dysmenorrhea rather than accepting it as normal — healthcare education campaigns (e.g., Endometriosis UK, World Endometriosis Research Foundation) are critical. Fertility preservation: women with endometriosis wishing to conceive should not delay attempting pregnancy after diagnosis, as disease progression and ovarian reserve decline over time (particularly with repeated ovarian surgery for endometriomas, which reduces functional ovarian tissue). Oophoropexy and minimal surgical intervention policy preserve ovarian reserve. Long-term hormonal suppression between pregnancies reduces symptomatic recurrence. Physiotherapy, psychological support (CBT), acupuncture, and pain management teams contribute to multidisciplinary endometriosis care and improved patient outcomes.