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

Endometriosis is a chronic inflammatory condition in which endometrial-like tissue (the tissue that normally lines the uterine cavity) grows outside the uterus — most commonly on the pelvic peritoneum, ovaries (endometriomas — 'chocolate cysts'), fallopian tubes, uterosacral ligaments, rectum, and bladder. This ectopic tissue responds to cyclic hormonal changes, bleeds during menstruation, and causes a local inflammatory reaction leading to adhesion formation, scarring, and progressive damage. Endometriosis affects approximately 10% of women of reproductive age — approximately 190 million women globally — making it one of the most common gynaecological conditions. Despite its prevalence, the average delay from symptom onset to diagnosis remains 7-8 years due to normalisation of dysmenorrhoea, lack of awareness, and the requirement for laparoscopic diagnosis. Endometriosis causes significant quality of life impairment through chronic pain and is associated with infertility — approximately 30-50% of women with endometriosis experience fertility difficulties.

The aetiology of endometriosis is incompletely understood, with multiple proposed and likely concurrent mechanisms. Retrograde menstruation (Sampson's theory): the most widely accepted theory — menstrual blood containing viable endometrial cells flows retrograde through the fallopian tubes into the peritoneal cavity, where cells implant and proliferate. However, retrograde menstruation occurs in most women, so additional factors are required for disease development in the 10% who develop endometriosis. Immune dysfunction: reduced peritoneal natural killer cell and macrophage clearance of retrograde endometrial cells — allowing ectopic implantation and survival. Genetic factors: endometriosis is heritable — first-degree relatives of affected women have a 7-fold increased risk; genome-wide association studies have identified multiple susceptibility loci. Coelomic metaplasia: transformation of peritoneal mesothelium into endometrial-like tissue. Stem cell theory. Inflammatory milieu: elevated peritoneal prostaglandins, cytokines (IL-6, TNF-alpha), oestrogen production from endometriotic lesions themselves, and aromatase activity in ectopic tissue perpetuate growth and pain.

Endometriosis classically presents with a triad of: dysmenorrhoea (painful periods — increasingly severe, progressive, and poorly responsive to standard analgesia), dyspareunia (deep pain during or after sexual intercourse), and chronic pelvic pain (non-menstrual, cyclical or constant). Symptom severity does not correlate with disease extent — stage 1 (minimal) endometriosis can cause severe pain, while stage 4 (severe) may be asymptomatic in some women. Additional symptoms: dyschezia (painful defaecation — particularly at menstruation, indicating bowel involvement), dysuria (painful urination — bladder endometriosis), urinary frequency, cyclical rectal bleeding or haematuria (rare — indicating bowel or bladder deeply infiltrating endometriosis), and subfertility. Endometriomas: ovarian cysts filled with old blood ('chocolate cysts') — often discovered on ultrasound or causing pelvic fullness/aching. Fatigue: a major but frequently underappreciated symptom — chronic pain, disrupted sleep, and systemic inflammation contribute. Mood disorders and depression: 6x higher prevalence of depression in endometriosis due to chronic pain, fertility implications, and diagnostic delay.

Endometriosis is a clinical and histological diagnosis — definitive diagnosis requires laparoscopy with direct visualisation and ideally biopsy for histological confirmation of endometrial glands and stroma outside the uterus. Clinical diagnosis: a careful history of the characteristic pain triad with worsening severity and menstrual pattern changes, combined with examination findings (uterine tenderness, fixed or retroverted uterus, nodularity in the recto-uterine pouch — Pouch of Douglas), provides strong clinical suspicion. NICE (2017) recommends that women with suspected endometriosis are NOT required to have diagnostic laparoscopy before empirical hormonal treatment is offered. Transvaginal ultrasound (TVUS): excellent for detecting ovarian endometriomas (characteristic 'ground glass' appearance) but has limited sensitivity for peritoneal lesions. MRI pelvis: the best non-invasive imaging for mapping deep infiltrating endometriosis (DIE) — particularly bowel and bladder involvement — critical for surgical planning. Staging: American Society for Reproductive Medicine (ASRM) classifies endometriosis Stage I-IV based on laparoscopic findings, but staging has limited correlation with symptoms or fertility outcomes. The ENZIAN classification provides more detailed anatomical mapping for DIE. CA-125: may be elevated but has poor specificity and sensitivity — not a diagnostic test.

Pain management — analgesia: NSAIDs (ibuprofen, naproxen) reduce prostaglandin-mediated dysmenorrhoea — most effective when started 1-2 days before expected menstruation. Paracetamol. Heat therapy. Hormonal suppression (creates a hypoestrogenic environment suppressing lesion growth and bleeding): combined oral contraceptive pill (OCP) continuous use — first-line medical treatment; levonorgestrel IUS (Mirena — effective for dysmenorrhoea and pelvic pain, particularly for suspected endometriosis in primary care); progestin-only therapy (norethisterone, medroxyprogesterone acetate, desogestrel); GnRH analogues (goserelin/leuprorelin — effective for pain, but hypoestrogenic side effects including bone loss require 'add-back' oestrogen therapy; licensed for 6-month courses); dienogest (GnRH analogue-level efficacy without add-back requirement — not yet widely available in all countries). Surgical treatment: laparoscopic excision (not ablation) of endometriotic lesions is the gold standard for definitive treatment — excision has lower recurrence rates than ablation. Conservative surgery preserves fertility. For deeply infiltrating endometriosis (bowel, bladder, ureter), surgery should be performed in a specialist endometriosis centre. Endometriomas: laparoscopic cystectomy preferred over drainage. IVF: recommended for endometriosis-related infertility — outcomes are generally good for Stage I-III; Stage IV has a modestly lower live birth rate. Definitive surgery (hysterectomy with bilateral salpingo-oophorectomy): only for women who have completed childbearing and have disease refractory to all other treatments — low-dose HRT may be continued.

The most significant complication of endometriosis is infertility — affecting 30–50% of women with the condition, caused by tubal adhesions, endometriomas reducing ovarian reserve, impaired oocyte quality, and altered endometrial receptivity. Endometriomas can rupture, causing acute abdominal pain, peritoneal contamination, and chemical peritonitis — requiring emergency laparoscopy. Deeply infiltrating endometriosis involving the bowel may cause partial or complete bowel obstruction; bladder or ureteral endometriosis can cause ureteric obstruction and obstructive nephropathy with progressive renal damage if undetected. A small but clinically important risk exists for malignant transformation of endometriomas into ovarian clear cell or endometrioid carcinoma (lifetime risk approximately 1–2% for endometrioma). Chronic pelvic pain leads to depression, anxiety, and impaired quality of life — psychosocial complications affect the majority of women with moderate-to-severe endometriosis. Adhesion formation from peritoneal inflammation and surgery creates risks of further bowel and urological complications. Recurrence after surgery is common — approximately 20–50% of women experience symptom recurrence within 5 years.

There is no established primary prevention for endometriosis. Reducing diagnostic delay is the most important public health intervention — earlier diagnosis enables earlier treatment to prevent progressive adhesion formation and fertility damage. Use of the combined OCP or progestogen-only methods from adolescence may reduce the number of menstrual cycles with retrograde flow and may slow disease progression, but does not prevent endometriosis from developing. For women already diagnosed: continuous hormonal suppression (avoiding hormone-free intervals) reduces recurrence of symptoms and lesions after surgery. Regular review with a specialist endometriosis team is important — the condition is chronic and management requirements change over time (particularly with fertility planning). Multidisciplinary support: psychological support (CBT, acceptance and commitment therapy) for chronic pain; pelvic floor physiotherapy; dietary modification (low FODMAP diet may reduce bloating and pain); and specialist support groups (Endometriosis UK, EndoFound) significantly improve quality of life.

See your GP or gynaecologist for: progressively worsening menstrual pain that limits daily activities or does not respond to standard analgesics (ibuprofen, paracetamol), pain during or after sex, non-menstrual pelvic pain, difficulty conceiving after 6-12 months of trying, or blood in urine or stool at menstruation. Do not accept being told 'painful periods are normal' — while some dysmenorrhoea is common, severe or progressive period pain is not something to simply endure and warrants investigation. Seek urgent assessment for: sudden severe pelvic pain (possible endometrioma rupture), signs of infection (fever, purulent discharge), or acute urinary or bowel obstruction symptoms (rare with advanced pelvic endometriosis). Women with known endometriosis experiencing a change in their pain pattern or symptoms should be reassessed — new deep pelvic pain, rectal bleeding, or urinary symptoms warrant repeat imaging to exclude disease progression or new complications.