Endometriosis: Causes, Symptoms and Treatment

Endometriosis is a chronic inflammatory condition in which tissue resembling the endometrium (the lining of the uterus) grows outside the uterus — in the pelvis, on the ovaries, fallopian tubes, peritoneum, bowel, bladder, and — rarely — beyond the pelvis. It affects approximately 10% of women of reproductive age, equivalent to approximately 190 million women worldwide.

Despite its prevalence, endometriosis remains dramatically underdiagnosed: the average time from first symptom to confirmed diagnosis is 7–10 years in most countries. This delay causes years of uncontrolled pain, preventable infertility, and significant psychological harm. Endometriosis is one of the leading causes of female infertility and chronic pelvic pain, and yet it remains poorly understood, under-researched, and often dismissed by healthcare providers.

What Is Endometriosis?

Mechanism

Endometriotic lesions are implants of endometrial-like glands and stroma that respond to the menstrual cycle — growing and shedding with each cycle. Unlike the uterine lining, which sheds through the cervix during menstruation, ectopic endometrial tissue has no exit route — it bleeds into the surrounding tissue, causing:

• Inflammation — cyclical bleeding triggers intense local inflammatory response
• Adhesions — fibrous scar tissue forms between pelvic organs (bowel adheres to ovary, fallopian tube to pelvic wall)
• Endometriomas — blood-filled cysts on the ovaries ("chocolate cysts" — dark brown old blood) that compress and damage ovarian tissue
• Nerve infiltration — deep lesions penetrate pelvic nerves, causing neuropathic pain

The Retrograde Menstruation Theory

The most widely accepted mechanism (Sampson's theory): during menstruation, some menstrual blood flows retrograde through the fallopian tubes into the peritoneal cavity; this endometrial tissue implants and proliferates. However, retrograde menstruation occurs in 90% of women, yet only 10% develop endometriosis — suggesting additional genetic, immunological, and microenvironmental factors determine whether implants survive and proliferate.

Endometriosis vs Adenomyosis

Adenomyosis — endometrial glands and stroma within the myometrium (muscle wall of the uterus); causes a diffusely enlarged, tender uterus; symptoms of heavy bleeding and dysmenorrhoea; diagnosed by MRI; frequently coexists with endometriosis. Important to distinguish as management differs: adenomyosis does not respond to excisional surgery; management is hormonal or ultimately hysterectomy.

Classification of Endometriosis

The rASRM (revised American Society for Reproductive Medicine) staging system classifies endometriosis I–IV by lesion number, size, and adhesion extent — but this does not correlate well with pain severity. The Endometriosis Fertility Index (EFI) better predicts fertility outcomes. The ENZIAN classification describes deep infiltrating endometriosis (DIE) lesions by anatomical compartment.

Type	Description	Key Features
Peritoneal (superficial)	Flat or slightly raised lesions on pelvic peritoneum	Powder-burn, red flame lesions; painful; may be subtle
Ovarian endometrioma	Endometriotic cyst within the ovary	Chocolate cyst; damages ovarian reserve
Deep infiltrating endometriosis (DIE)	Penetrates >5 mm below peritoneal surface	Uterosacral ligaments, rectovaginal septum, bowel, bladder; most painful

Symptoms

Dysmenorrhoea (Painful Periods)

The cardinal symptom — but critically, not all painful periods indicate endometriosis, and not all endometriosis causes painful periods. Features that raise suspicion:

• Pain begins 1–2 days before menstruation (primary dysmenorrhoea is usually only on day 1–2)
• Pain is severe — interfering with school, work, or daily activities; not adequately controlled by standard NSAIDs
• Pain is progressive — worsening over years (unlike primary dysmenorrhoea which often improves with age/OCP)
• Associated with dyschezia (painful bowel movements) at menstruation — suggests posterior DIE

Chronic Pelvic Pain (CPP)

Pain outside of menstruation — present throughout the cycle; dull, aching pelvic and lower back pain; worse with standing, intercourse, or physical exertion. Central sensitisation contributes — chronic nociceptive input from endometriotic lesions sensitises the central nervous system, leading to widespread pain hypersensitivity.

Dyspareunia (Painful Intercourse)

Pain during or after deep vaginal penetration (deep dyspareunia) — highly suggestive of posterior DIE involving the uterosacral ligaments, rectovaginal septum, or pouch of Douglas. Severe dyspareunia profoundly impacts intimate relationships and quality of life.

Cyclical Bowel and Bladder Symptoms

• Dyschezia — painful defaecation, particularly at menstruation; rectal urgency; altered bowel habit; from posterior DIE involving the rectum or recto-sigmoid
• Cyclical rectal bleeding — from bowel endometriosis mucosa penetration
• Cyclical dysuria / haematuria — bladder endometriosis; cyclical urinary frequency and urgency; voiding difficulty
• Cyclical shoulder tip pain — diaphragmatic endometriosis (rare); pleural endometriosis with catamenial pneumothorax

Infertility

Endometriosis is responsible for approximately 25–50% of cases of female infertility. Mechanisms:

• Endometriomas — bilateral ovarian cysts damage follicular reserve (primordial follicle loss); reduce AMH; impair oocyte quality; respond poorly to ovarian stimulation
• Pelvic adhesions — fallopian tube distortion and obstruction; impaired ovum pick-up
• Peritoneal environment — inflammatory mediators, activated macrophages, and prostaglandins in peritoneal fluid impair sperm function and embryo implantation
• Implantation defect — endometriosis alters endometrial receptivity

Fatigue

Profound, disabling fatigue is consistently reported by women with endometriosis — partly from chronic pain and disrupted sleep, and partly from the systemic inflammatory burden of the disease.

Diagnosis

The Diagnostic Delay Problem

The average 7–10 year diagnostic delay results from multiple factors:

• Symptoms normalised by both patients and clinicians ("bad periods are normal")
• Endometriosis has no reliable non-invasive diagnostic biomarker (CA125 is unreliable)
• Definitive diagnosis historically required laparoscopy with histological confirmation
• Symptoms overlap with IBS, UTI, and primary dysmenorrhoea — leading to misdiagnosis

Clinical Diagnosis

A thorough history (symptom pattern, severity, relationship to cycle) and examination (vaginal tenderness, uterosacral nodularity on bimanual examination) are essential. Clinical suspicion warrants investigation — empirical medical treatment is appropriate without laparoscopic confirmation if clinical suspicion is high.

Transvaginal Ultrasound (TVUS)

Ovarian endometriomas: characteristic homogeneous ground-glass appearance on ultrasound — highly reliable (sensitivity/specificity >95%). TVUS with bowel preparation by an experienced operator (IOTA/IDEA consensus approach) can reliably detect posterior deep endometriosis (rectosigmoid, rectovaginal septum).

MRI Pelvis

The superior imaging modality for deep infiltrating endometriosis — maps DIE extent across all pelvic compartments (bladder, uterosacral ligaments, rectovaginal septum, bowel, lateral parametria), providing a roadmap for surgical planning. Essential before complex excisional surgery. Cannot detect superficial peritoneal lesions.

Diagnostic Laparoscopy

The historical gold standard — direct visualisation of endometriotic lesions (red, blue/black, or white lesions; endometriomas; adhesions; deeply infiltrating disease) with biopsy and histological confirmation. Enables simultaneous surgical treatment. Modern guidelines acknowledge that empirical medical treatment may be initiated on clinical grounds alone without laparoscopy, reserving surgery for diagnostic uncertainty, treatment failure, or women seeking surgical management.

Treatment

Endometriosis is a chronic disease — treatment aims to control symptoms, prevent progression, preserve fertility, and improve quality of life. There is no cure except menopause (or total hysterectomy with bilateral oophorectomy, which induces surgical menopause).

Medical Management (Hormonal Suppression)

All effective medical treatments work by suppressing ovarian hormone production — reducing oestrogen-driven endometriosis activity:

Combined Oral Contraceptive Pill (COCP)

First-line medical treatment — continuous (no pill-free break) or cyclical; reduces dysmenorrhoea in approximately 70–80% of women. Well-tolerated, inexpensive, reversible. Does not eliminate endometriosis but suppresses lesion activity and prevents new lesion formation while taken.

Progestogens

• Norethisterone, medroxyprogesterone acetate, dydrogesterone — oral progestogens; suppress endometrial tissue; effective for pain
• Levonorgestrel IUS (Mirena) — intrauterine system providing local progestogen; induces endometrial atrophy; effective for dysmenorrhoea and CPP; reduces period volume; does not address ovarian endometriomas or deep disease
• Desogestrel (progestogen-only pill) — continuous pill; induces amenorrhoea; effective pain control

GnRH Agonists (Leuprorelin, Goserelin, Buserelin)

Induce a pseudomenopausal state — profound oestrogen suppression; effective for all forms of endometriosis pain. Add-back HRT (low-dose oestrogen + progestogen) given concurrently prevents bone loss and menopausal symptoms while maintaining efficacy. Duration limited to 6–12 months without add-back; with adequate add-back, can be used longer.

Oral GnRH Antagonists (Elagolix, Linzagolix, Relugolix)

Newer oral once-daily agents — immediate and reversible hormone suppression without initial flare (unlike GnRH agonists); given with add-back; approved for endometriosis pain in several countries. ORILISSA (elagolix) trial: significant reduction in dysmenorrhoea and non-menstrual pelvic pain vs placebo.

Dienogest

Selective progestogen with anti-androgenic properties — approved for endometriosis in Europe and Asia; continuous administration; effective pain control; induces endometrial atrophy; good tolerability; widely used in China and Japan.

Surgical Management

Surgery is indicated for: failed medical treatment, desire to preserve/improve fertility, diagnostic uncertainty, large endometriomas, or significant bowel/bladder involvement.

Laparoscopic Excision of Endometriosis

The preferred surgical approach — excision (cutting out) of endometriotic lesions is superior to ablation (burning/vaporising) for deep lesions and symptom relief. Specialist endometriosis surgeons excise peritoneal lesions, uterosacral ligament DIE, and deep rectovaginal and bladder disease.

For rectosigmoid endometriosis — depending on depth and extent:

• Shaving / disc excision — for superficial bowel involvement; preserves bowel continuity
• Segmental bowel resection — for full-thickness involvement; followed by anastomosis; performed by combined gynaecologist + colorectal surgical team

Laparoscopic excision at specialist centres achieves 70–80% pain improvement; recurrence rates approximately 20–30% over 5 years.

Laparoscopic Cystectomy for Ovarian Endometrioma

Excision (stripping) of the endometrioma cyst wall — superior to drainage/ablation; lower recurrence rates. Important consideration: cystectomy inevitably removes some normal ovarian cortex and damages ovarian reserve (reduces AMH); for women planning fertility, the risk-benefit must be carefully balanced. Bilateral ovarian cystectomies carry particular risk of irreversible ovarian failure.

Hysterectomy + Bilateral Salpingo-Oophorectomy

The only definitive cure — reserved for women who have completed childbearing, have severe symptoms refractory to all other treatments, and accept surgical menopause. Oophorectomy (removal of ovaries) is necessary to eliminate endometriosis-driving oestrogen; HRT is required post-operatively. Recurrence risk without oophorectomy is 15–20%.

Fertility Treatment

For women with endometriosis-related infertility:

• IUI (intrauterine insemination): may be tried in mild-moderate endometriosis without tubal factor; limited efficacy
• IVF (in vitro fertilisation): the most effective fertility treatment for endometriosis — particularly stage III–IV, bilateral endometriomas, or tubal disease; live birth rates comparable to tubo-peritoneal factor infertility if ovarian reserve is adequate

To operate or not before IVF: controversial. For small endometriomas (<4 cm) with normal ovarian reserve — IVF without prior cystectomy may be preferable to protect residual reserve. For large symptomatic endometriomas — surgery before IVF improves access and response.

Holistic Management

Pain management beyond hormonal therapy:

• NSAIDs: mefenamic acid, ibuprofen — first-line for dysmenorrhoea
• Neuropathic agents: gabapentin, amitriptyline — for central sensitisation and neuropathic pain components
• Physiotherapy: pelvic floor physiotherapy for hypertonic pelvic floor (common in chronic pelvic pain); significantly reduces musculoskeletal pain contribution
• Psychological support: CBT, mindfulness, pain psychology — essential for managing chronic pain; reduces pain catastrophising and improves coping

Endometriosis Care in China

China's gynaecology centres offer:

• Specialist endometriosis assessment: transvaginal ultrasound (IOTA/IDEA protocol) and MRI pelvis for deep infiltrating endometriosis mapping; multidisciplinary endometriosis clinics
• Dienogest and oral GnRH antagonist prescribing: advanced hormonal suppression — drugs widely available in China
• Laparoscopic excision surgery: specialist endometriosis surgeons with experience in DIE excision, rectovaginal and uterosacral endometriosis; combined gynaecology-colorectal teams for bowel endometriosis
• Laparoscopic ovarian cystectomy: endometrioma excision with reserve-preserving technique; intraoperative AMH and reserve assessment
• IVF for endometriosis-related infertility: full IVF services at reproductive medicine centres; excellent laboratory and clinical outcomes
• Cost: care in China is generally less expensive than UK private treatment, but the hospital prices each case individually — ask us for the written quote before you commit.
• Full English care navigation from diagnostic assessment through hormonal management, surgical planning, and fertility treatment

Contact a ChinaMedicalTour care navigator to arrange an endometriosis assessment, laparoscopy consultation, or IVF programme.

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Medical content based on MSD Manuals and international endometriosis guidelines (ESHRE, ACOG, NICE). Evidence reviewed 2025.

Frequently Asked Questions

Can international patients submit pelvic ultrasound or MRI scans for endometriosis review?

Yes. High-resolution pelvic MRI scans and ultrasound reports can be submitted for pre-consultation review by Chinese gynecological surgeons specializing in deep infiltrating endometriosis (DIE).

What surgical and medical management strategies are evaluated for endometriosis?

Specialized centers evaluate laparoscopic excision of endometriotic lesions, ovarian cystectomy, nerve-sparing pelvic dissection, and hormonal suppression therapies tailored to symptom severity and fertility goals.

How are consultations and post-operative follow-up coordinated?

Coordination covers specialist outpatient booking, inpatient surgical scheduling, translation support, and detailed post-operative recovery guidance confirmed with the treating physician.