Residency · Residency · Obstetrics Gynecology

Endometriosis: Diagnosis, Medical Therapy, and Surgical Principles

Overview

Endometriosis is defined by the presence of endometrial-like tissue (glands and stroma) outside the uterine cavity. It affects 6 to 10% of reproductive-age women, up to 50% of women with infertility, and 70 to 80% of women with chronic pelvic pain. It is an estrogen-dependent chronic inflammatory condition with a significant diagnostic delay, averaging 7 to 10 years from symptom onset to diagnosis.

Pathogenesis Theories

The most widely accepted theory is retrograde menstruation (Sampson theory), in which menstrual tissue refluxes through the fallopian tubes and implants on peritoneal surfaces. The coelomic metaplasia theory proposes that peritoneal mesothelium transforms into endometrial-like tissue. Lymphatic and vascular dissemination explains distant implants such as thoracic endometriosis. The stem cell theory suggests that bone marrow-derived stem cells differentiate into endometrial tissue. Immune dysfunction, specifically failure to clear ectopic endometrial cells, allows implantation and growth.

Common Locations

Pelvic sites include the ovaries (the most common location), uterosacral ligaments, posterior cul-de-sac, broad ligament, anterior cul-de-sac (vesicouterine fold), and fallopian tubes. Deep infiltrating endometriosis involves the rectovaginal septum, bowel wall, bladder wall, and ureters. Extrapelvic disease is rare but can involve the diaphragm (causing catamenial pneumothorax), abdominal wall surgical scars, vagina, cervix, lungs, and central nervous system.

Clinical Presentation

Symptoms

Dysmenorrhea is the most common symptom and is typically progressive, often starting before menses. Chronic pelvic pain frequently includes a non-cyclical component. Deep dyspareunia occurs especially with posterior involvement. Dyschezia (painful bowel movements) is most prominent during menses. Dysuria occurs with bladder involvement. Infertility may be the sole presenting complaint. Catamenial symptoms including cyclic shoulder pain, pneumothorax, hemoptysis, or rectal bleeding occur with involvement of the respective organs. Importantly, symptom severity does not correlate with disease stage.

Physical Exam

The exam may be entirely normal in many patients. When findings are present, they may include tender nodularity of the uterosacral ligaments (best assessed during menses), a fixed retroverted uterus, adnexal mass (endometrioma), and rarely visible vaginal or cervical lesions.

<image>Anatomic diagram of the female pelvis showing common endometriosis implant locations: ovarian endometriomas, peritoneal implants on the uterosacral ligaments and posterior cul-de-sac, deep infiltrating disease in the rectovaginal septum and bowel wall, and bladder peritoneum, with relative frequency percentages for each site</image>

Diagnosis

Clinical Diagnosis

High clinical suspicion based on history and exam is often sufficient to initiate empiric treatment. Definitive diagnosis has historically required surgical confirmation via laparoscopy with biopsy, but the trend is moving toward clinical and imaging-based diagnosis without requiring surgery.

Imaging

Transvaginal ultrasound is the first-line imaging modality. Ovarian endometriomas appear as cysts with homogeneous, low-level internal echoes, described as a "ground glass" appearance, with approximately 90% sensitivity. Specialized sonographic evaluation can detect deep infiltrating endometriosis involving bowel, bladder, and uterosacral ligaments, though this is operator-dependent. Superficial peritoneal disease is not detectable on ultrasound. MRI is excellent for characterizing deep infiltrating endometriosis of the rectovaginal septum, bladder, and ureters and is useful for surgical planning. On T1-weighted images with fat suppression, endometriomas appear hyperintense. MRI is not necessary for all patients and should be reserved for complex or deep disease.

Surgical Diagnosis

Laparoscopy remains the gold standard for diagnosis. Visual findings include powder-burn (dark), red, white, or clear vesicular lesions. Histologic confirmation showing endometrial glands and stroma on biopsy is ideal but not always seen; visual diagnosis is accepted. The role of diagnostic laparoscopy is declining, and many guidelines now support empiric treatment based on symptoms.

Biomarkers

CA-125 may be mildly elevated above 35 U/mL but is neither sensitive nor specific enough for diagnosis. No validated non-invasive diagnostic biomarker currently exists. Research into miRNA, metabolomic, and proteomic biomarkers is ongoing.

Staging (rASRM Classification)

Stage I (minimal) involves isolated implants with no significant adhesions. Stage II (mild) shows superficial implants with some adhesions. Stage III (moderate) includes deep implants, endometriomas, and moderate adhesions. Stage IV (severe) involves large endometriomas, dense adhesions, and cul-de-sac obliteration. A major limitation of this staging system is that it does not correlate well with symptom severity or fertility outcomes. The ENZIAN classification supplements the rASRM system by describing the extent of retroperitoneal deep infiltrating disease.

Medical Therapy

Principles

Medical therapy suppresses estrogen-dependent disease activity but does not eradicate the disease; symptoms typically recur after discontinuation. It cannot improve anatomic distortion from adhesions or endometriomas. It is the first-line treatment for pain and can be started empirically.

NSAIDs

NSAIDs provide symptomatic relief of dysmenorrhea but are not disease-modifying and are often insufficient as sole therapy.

Hormonal Contraceptives

Combined oral contraceptives used continuously (skipping the placebo week) are more effective than cyclic use. Progestin-only pills, typically norethindrone acetate 5 mg daily, are effective for pain. Depot medroxyprogesterone acetate at 150 mg intramuscularly every 12 weeks induces amenorrhea. The levonorgestrel IUD (Mirena) is effective for pelvic pain and dysmenorrhea and is especially useful post-surgery to prevent recurrence. The etonogestrel implant (Nexplanon) has limited data but may be beneficial.

GnRH Agonists

Leuprolide depot at 3.75 mg intramuscularly monthly or 11.25 mg every 3 months creates a medical menopause through profound estrogen suppression. Add-back therapy with norethindrone acetate 5 mg daily is mandatory for use beyond 6 months to prevent bone loss and vasomotor symptoms without stimulating endometriosis. These agents are highly effective for pain. The typical duration is 6 to 12 months.

GnRH Antagonists (Oral)

Elagolix (Orilissa) is available at 150 mg daily for moderate pain (providing partial estrogen suppression) or 200 mg twice daily for severe pain and dyspareunia (providing greater suppression). The higher dose is limited to 6 months without add-back due to bone loss; the lower dose can be used up to 24 months. These oral agents offer rapid onset and offset, dose-dependent estrogen suppression, and represent a significant advance over injectable GnRH agonists.

Aromatase Inhibitors

Letrozole or anastrozole block peripheral and local estrogen production. They are used in combination with other hormonal therapy (oral contraceptives, progestins, or GnRH agonists) to avoid ovarian cyst formation. They are reserved for refractory disease and are not first-line, with limited evidence in endometriosis.

Danazol

Danazol is an androgenic agent that was historically used but has been largely abandoned due to its androgenic side effects including acne, hirsutism, weight gain, and voice deepening.

<image>Stepwise medical management algorithm for endometriosis pain: first-line with NSAIDs and combined hormonal contraceptives (continuous use), second-line with progestins (norethindrone, DMPA, LNG-IUD), third-line with GnRH agonists or oral GnRH antagonists (elagolix), and fourth-line with aromatase inhibitors for refractory disease</image>

Surgical Management

Indications

Surgery is indicated for failed medical therapy, endometriomas larger than 4 cm (due to symptoms, diagnostic uncertainty, or impact on ovarian reserve), deep infiltrating endometriosis causing organ dysfunction such as bowel obstruction or ureteral compression, infertility (especially stage III to IV), and the need for tissue diagnosis.

Laparoscopic Surgery

Excision (resection) is preferred over ablation because it removes the full depth of the lesion, provides tissue for histology, and may have lower recurrence rates, though this remains somewhat controversial. Ablation (cauterization or vaporization) destroys only surface disease, may not address deep involvement, and provides no tissue for histology. For deep infiltrating endometriosis, excision is essential.

For endometrioma management, cystectomy (excision of the cyst wall) is preferred because it has lower recurrence than drainage and ablation. However, cystectomy carries a risk of removing healthy ovarian tissue, potentially impacting ovarian reserve. Drainage and ablation of the cyst wall is an alternative in women with diminished reserve. Adhesiolysis restores normal anatomy, though lysed adhesions may reform.

Deep infiltrating endometriosis surgery requires expertise in ureteral dissection, bowel resection (segmental or shaving/disc excision), and bladder resection. A multidisciplinary team including a gynecologist, colorectal surgeon, and urologist is often needed. Preoperative imaging with MRI or specialized ultrasound is essential for surgical planning.

Hysterectomy

Hysterectomy is considered for refractory endometriosis-related pain when fertility is not desired. Bilateral salpingo-oophorectomy may be performed to eliminate the estrogen source and decrease recurrence, but it carries the risk of surgical menopause in young women and requires hormone replacement therapy. Low-dose estrogen after bilateral salpingo-oophorectomy for endometriosis is generally safe, with a small recurrence risk. Hysterectomy with ovarian conservation may not completely resolve symptoms if the ovaries continue producing estrogen. Excision of all visible disease at the time of hysterectomy improves outcomes.

Post-Surgical Medical Therapy

Hormonal suppression after conservative surgery reduces recurrence. A levonorgestrel IUD or continuous combined oral contraceptives for at least 6 to 18 months post-surgery is recommended.

Endometriosis and Infertility

Endometriosis impairs fertility through anatomic distortion (adhesions, tubal obstruction), an inflammatory peritoneal environment, impaired oocyte quality, and altered endometrial receptivity. For stage I to II disease, surgery for infertility shows modest benefit, as demonstrated in the Marcoux randomized controlled trial (NNT of 12). For stage III to IV disease, surgery restores anatomy and improves both natural and IVF-related fertility. IVF is often recommended for moderate to severe endometriosis, especially with other contributing factors. GnRH agonist treatment for 3 to 6 months before IVF may improve outcomes based on systematic review data. The decision about endometrioma surgery before IVF requires weighing the benefit of cyst removal against the risk of reducing ovarian reserve.

Clinical Pearls

Symptom severity does not correlate with disease stage. A patient with minimal disease can have severe pain.

Empiric treatment with hormonal therapy is acceptable without surgical confirmation. Diagnostic laparoscopy is no longer required before treatment.

Continuous combined oral contraceptive use (skipping the placebo) is more effective than cyclic use for endometriosis pain.

Oral GnRH antagonists (elagolix) offer the efficacy of GnRH agonists with the convenience of an oral pill and rapid reversibility.

Excision of endometriosis is preferred over ablation, especially for deep disease, as it provides histologic confirmation and more complete treatment.

Endometrioma cystectomy has lower recurrence than drainage and ablation but carries a risk of diminishing ovarian reserve. This tradeoff should be discussed with patients.

Post-surgical hormonal suppression with a levonorgestrel IUD or continuous oral contraceptives significantly reduces pain recurrence. Always plan for post-operative medical management.

Hysterectomy with bilateral salpingo-oophorectomy is not a guaranteed cure. Realistic expectations should be discussed with patients.

References

• ACOG Practice Bulletin No. 114: Management of Endometriosis (2010, reaffirmed 2022)
• ESHRE Guideline: Endometriosis (2022)
• Taylor HS et al. Treatment of endometriosis-associated pain with elagolix. N Engl J Med. 2017;377:28-40
• Dunselman GA et al. ESHRE guideline: management of women with endometriosis. Hum Reprod. 2014;29:400-412
• Hart RJ et al. Excisional surgery versus ablative surgery for ovarian endometriomata. Cochrane Database Syst Rev. 2008
• Marcoux S et al. Laparoscopic surgery in infertile women with minimal or mild endometriosis. N Engl J Med. 1997;337:217-222
• Zondervan KT et al. Endometriosis. N Engl J Med. 2020;382:1244-1256

Read this lecture as Markdown