Endometriosis: Symptoms, Diagnosis & Treatment Options

A Disease That Takes a Decade to Diagnose

Endometriosis affects an estimated 190 million women and girls of reproductive age globally — roughly 10% of the female population — yet the average time from symptom onset to confirmed diagnosis is 7–10 years in high-income countries, with some studies reporting up to 11 years in the United Kingdom. This diagnostic delay is not explained by rarity or obscurity. It persists because pelvic pain has been historically normalized in young women, because symptoms overlap with irritable bowel syndrome and other conditions, and because the gold-standard diagnostic test requires surgery.

The condition involves endometrial-like tissue growing outside the uterus — on the ovaries, fallopian tubes, peritoneum, bowel, bladder, and in rare cases the lungs and diaphragm. These implants respond to menstrual cycle hormones, proliferating during the luteal phase and breaking down during menstruation, producing inflammation, adhesions, and pain that bears no reliable correlation to lesion extent.

What Causes Endometriosis: Competing Theories

Retrograde menstruation, proposed by John Sampson in the 1920s, remains the dominant hypothesis: menstrual blood flows backward through the fallopian tubes, depositing endometrial cells on pelvic structures where they implant and proliferate. Supporting evidence includes the fact that 90% of menstruating women have detectable retrograde flow — suggesting that immune dysfunction preventing normal clearance of ectopic cells is the critical cofactor.

The coelomic metaplasia theory proposes that peritoneal cells undergo metaplastic transformation into endometrial-like tissue under hormonal or inflammatory stimulation, explaining rare cases of endometriosis in men and prepubertal girls where retrograde menstruation is impossible. Stem cell theory, gaining traction since the 2010s, proposes that endometrial stem/progenitor cells from bone marrow or circulating blood seed distant sites, accounting for extrapelvic disease.

• Retrograde menstruation: anatomical basis; immune clearance failure is co-required
• Coelomic metaplasia: explains cases outside typical pelvic anatomy
• Stem cell dissemination: explains thoracic and distal endometriosis
• Genetic predisposition: first-degree relatives have 7-fold increased risk; heritability estimated at 47–51%

Symptoms: Variable, Cyclical, and Frequently Dismissed

Pain is the cardinal symptom, but its character and timing vary substantially. Dysmenorrhea (painful menstruation) not relieved by standard analgesics affects 71–87% of patients. Dyspareunia (pain with intercourse) occurs in 40–50%, typically with deep penetration and posterior cul-de-sac involvement. Dyschezia (painful defecation) suggests bowel involvement, present in approximately 32% of cases.

Approximately 20–25% of women with endometriosis are asymptomatic, discovered incidentally during surgery for other conditions. Conversely, some women with minimal disease by surgical staging have severe symptoms — reinforcing that symptom severity and anatomical burden are poorly correlated.

Diagnosis: Why Surgery Is Still Required

Laparoscopy with histological confirmation of biopsied tissue remains the gold standard for definitive diagnosis. No blood test, imaging study, or symptom questionnaire has sufficient sensitivity and specificity to replace surgical diagnosis. CA-125, a tumor marker elevated in endometriosis, has poor sensitivity (28–40% in stage I-II disease) and is elevated in multiple other conditions including ovarian cancer and fibroids.

Transvaginal ultrasound (TVUS) reliably identifies ovarian endometriomas (chocolate cysts) — accuracy exceeds 90% — but misses most peritoneal implants and superficial lesions. MRI performs better for deeply infiltrating endometriosis, with sensitivity of 77% and specificity of 89% for bowel endometriosis in expert hands, but depends heavily on operator experience. Neither replaces laparoscopy for staging according to the revised American Society for Reproductive Medicine (rASRM) classification system (Stage I–IV based on lesion extent and adhesions).

Hormonal Treatment Options

Hormonal suppression is the mainstay of medical management, operating on the principle that endometriotic implants — like eutopic endometrium — are hormone-dependent and regress in low-estrogen or progestin-dominant environments. No medical therapy eliminates endometriosis; all options manage symptoms and aim to slow progression.

• Combined oral contraceptives (COCs): first-line for pain management; significantly reduce dysmenorrhea; continuous use (no placebo interval) preferred for suppression
• Levonorgestrel-releasing IUS (Mirena): reduces heavy menstrual bleeding and pelvic pain; local progestin effect; duration of 5–7 years
• Progestins (norethindrone acetate, dienogest): dienogest 2 mg daily shows efficacy comparable to GnRH agonists with a better side effect profile; approved for endometriosis in Europe and Japan
• GnRH agonists (leuprolide, goserelin): create medically induced menopause; highly effective for pain; limited to 6 months without add-back hormone therapy due to bone loss
• GnRH antagonists (elagolix): FDA-approved 2018; oral once-daily; dose-dependent estrogen suppression; more flexible dosing than agonists

Surgical excision of lesions provides longer-lasting pain relief than ablation (vaporization) in most studies, with recurrence rates of approximately 20% at 5 years following complete excision versus 40–50% following ablation. The choice of surgeon experience and technique is a major determinant of outcome.

This article is for informational purposes only. Consult a qualified healthcare professional.