Endometriosis
Endometriosis is a disease in which tissue similar to the lining of the uterus grows outside the uterus. It grows most often on the ovaries, the fallopian tubes, the peritoneum (the lining of the pelvis), and the ligaments behind the uterus. It is a chronic inflammatory disease. It is common in women of reproductive age. It is also a major cause of pelvic pain and of infertility in couples seeking care.1 Its prevalence, or how common it is, remains hard to measure. The estimate shifts with the population studied and with how a case is defined and detected.2 The delay in diagnosis is long either way. The median time from first symptoms to diagnosis often exceeds 7 to 9 years.3 Half of women wait longer still. Much of that delay comes from treating severe period pain as normal.4 The disease causes inflammation, scar tissue (adhesions), and distortion of normal pelvic anatomy. It can block the fallopian tubes and make implantation of an embryo more difficult. These effects harm a woman's health and a couple's fertility.5 Excision surgery removes the disease by cutting it out. The surgeon works through small incisions with a camera and removes each lesion. Results from many centers show clear improvements in pain and quality of life after excision.67 Hormonal medications given after surgery can reduce pain. They can also reduce how often symptoms and ovarian cysts return.8 These medications do not remove disease that is already present. They do not restore pelvic anatomy that the disease has already distorted.9 When the medications stop, the disease usually becomes active again.10 Severe disease can bind the pelvic organs together. In these cases, some surgeons use methods designed to remove the disease, restore normal anatomy, and prevent new scar tissue. Three of these methods are defined here: PEARS, NARPS, and S-MAP.11
The origin of endometriosis is still an open question. The leading theory came from Sampson in 1927. He proposed that menstrual tissue flows backward through the fallopian tubes and implants in the pelvis.12 This theory, retrograde menstruation, has shaped medical thinking for nearly a hundred years. It cannot explain the whole disease.13 The disease appears in places that backward flow cannot reach. It occurs outside the pelvis. Tissue similar to the uterine lining has been found in female fetuses at autopsy.14 It has been reported in male patients given high doses of estrogen.1516 Researchers have proposed other explanations. One is coelomic metaplasia, in which pelvic cells change type. Another is embryonic rest and Mullerianosis, tissue left over from early development. Others include stem cells seeding new sites and spread through blood and lymph vessels.17 Retrograde menstruation does not stand on its own as the cause of the disease.18
Can ultrasound detect endometriosis? The answer depends on the type of disease. A skilled transvaginal ultrasound can detect endometriomas, ovarian cysts filled with old blood. It can also detect deep lesions. It often misses the small, superficial lesions on the peritoneum that drive many women's symptoms. A normal scan does not rule out the disease.192021 Laparoscopy, surgery through small incisions with a camera, remains the most thorough way to map the disease. It is the only way to confirm it under a microscope.22 Imaging guidelines now accept expert ultrasound or MRI to diagnose ovarian cysts and deep disease. Superficial disease still requires surgery to confirm.22 The severity of symptoms does not track with the stage of the disease.23 Severe, life-limiting pain can come from stage I disease.23 In one study of more than 1,000 women, the association between stage and pelvic pain was weak and inconsistent. Stage IV disease does not reliably mean a heavier symptom burden. Some women with severe disease present with infertility rather than pain.23 The stage number alone tells a clinician little about a woman's symptoms or her fertility risk.
Medications can suppress endometriosis. They do not remove it, and they do not cure it.5 Hormonal medications can ease symptoms and shrink some lesions while a woman takes them. No medication removes lesions that are already present. No medication reverses the disease permanently.24 The decision whether and when to operate is individual. It rests on symptoms, fertility goals, and the extent of the disease. Excision cuts the lesion out. Ablation burns the surface of the lesion. Comparative data favor excision over ablation for period pain, painful bowel movements, and ongoing pelvic pain.7 In published series, complete excision by an experienced surgeon is associated with fewer repeat operations. Reported recurrence rates vary widely. They depend on the severity of disease, the types of lesions present, and the length of follow-up. For this reason, each case requires individual judgment.2526 Surgery removes the disease that is present. The disease can still return. Excision provides durable control rather than a guaranteed permanent cure.27
Endometriosis reaches beyond the pelvis and into the nervous system. The disease can alter the nerves that carry pain signals. The pelvic nerves grow more sensitive over time. The spinal cord and brain then become more sensitive as well. This process sustains pain over the long term.28 Pain that persists after excision can come from these nerve changes rather than from remaining disease.29 Effective pain care often requires more than surgery. Pelvic floor physical therapy and daily habits both matter.30 Endometriosis is a whole-body inflammatory disease with a disordered immune response.31 Women with endometriosis also have high rates of other conditions. These include fibromyalgia, chronic fatigue syndrome, autoimmune disease, and hormonal disorders. The effects of the disease reach well beyond the pelvis.32 The disease is associated with a lower ovarian reserve and may affect egg quality over time.33 This association is one reason couples benefit from an early evaluation rather than a long wait.34 The luteal phase, the second half of the cycle, can be affected as well. This effect adds another problem beyond the altered pelvic anatomy.35 Many women told they have "unexplained" infertility are in fact undiagnosed. Careful laparoscopic evaluation often finds disease that earlier imaging missed.36
Cited in this entry
- Zondervan KT, Becker CM, Missmer SA Endometriosis. The New England journal of medicine. 2020. https://pubmed.ncbi.nlm.nih.gov/32212520/
- Shafrir AL, Farland LV, Shah DK, et al. Risk for and consequences of endometriosis: a critical epidemiologic review. Best Practice & Research Clinical Obstetrics & Gynaecology. 2018. https://pubmed.ncbi.nlm.nih.gov/30017581/
- Management of endometriosis in general practice: the pathway to diagnosis. https://pubmed.ncbi.nlm.nih.gov/17550672/
- Ballard K, Lowton K, Wright J What's the delay? A qualitative study of women's experiences of reaching a diagnosis of endometriosis. Fertility and sterility. 2006. https://pubmed.ncbi.nlm.nih.gov/17070183/
- Giudice LC Clinical practice. Endometriosis. The New England journal of medicine. 2010. https://pubmed.ncbi.nlm.nih.gov/20573927/
- Yeung P Jr, Tu F, Bajzak K, Lamvu G, Guzovsky O, Agnelli R et al. A pilot feasibility multicenter study of patients after excision of endometriosis. JSLS : Journal of the Society of Laparoendoscopic Surgeons. 2013. https://pubmed.ncbi.nlm.nih.gov/23743377/
- Laparoscopic Excision Versus Ablation for Endometriosis. https://pubmed.ncbi.nlm.nih.gov/28456617/
- Zakhari A, Delpero E, McKeown S, Tomlinson G, Bougie O, Murji A Endometriosis recurrence following post-operative hormonal suppression: a systematic review and meta-analysis. Human reproduction update. 2021. https://pubmed.ncbi.nlm.nih.gov/33020832/
- Vercellini P, Viganò P, Somigliana E, Fedele L Endometriosis: pathogenesis and treatment. Nature reviews. Endocrinology. 2014. https://pubmed.ncbi.nlm.nih.gov/24366116/
- Guo SW Recurrence of endometriosis and its control. Human reproduction update. 2009. https://pubmed.ncbi.nlm.nih.gov/19279046/
- Hilgers TW. Chapter 73: PEARS for Extensive Pelvic Adhesive Disease. The Medical and Surgi. https://rrmacademy.org/library/chapter-73-pears-for-extensive-pelvic-adhesive-disease-recuj1rmnmcabnusz/
- Yovich JL, Rowlands PK, Lingham S, Sillender M, Srinivasan S Pathogenesis of endometriosis: Look no further than John Sampson. Reproductive biomedicine online. 2020. https://pubmed.ncbi.nlm.nih.gov/31836436/
- Roychoudhury S, Buza N Endometriosis Then and Now: A 100-Year Journey Around Pathogenesis and Clinicopathologic Associations. Archives of pathology & laboratory medicine. 2025. https://pubmed.ncbi.nlm.nih.gov/41429178/
- Signorile PG, Baldi F, Bussani R, et al. New evidence of the presence of endometriosis in the human fetus. Reprod Biomed Online. 2010;21(1):142-7. PMID: 20471320. https://pubmed.ncbi.nlm.nih.gov/20471320/
- Andres MP, Arcoverde FVL, Souza CCC, Fernandes LFC, Abrão MS, Kho RM Extrapelvic Endometriosis: A Systematic Review. Journal of minimally invasive gynecology. 2020. https://pubmed.ncbi.nlm.nih.gov/31618674/
- Rei C, Williams T, Feloney M. Endometriosis in a Man as a Rare Source of Abdominal Pain: A Case Report and Review of the Literature. Case Rep Obstet Gynecol. 2018;2018:2083121. PMID: 29670782. https://pubmed.ncbi.nlm.nih.gov/29670782/
- Lamceva J, Uljanovs R, Strumfa I. The Main Theories on the Pathogenesis of Endometriosis. Int J Mol Sci. 2023;24(5):4254. PMID: 36901685. https://pmc.ncbi.nlm.nih.gov/articles/PMC10001466/
- Sourial S, Tempest N, Hapangama DK Theories on the pathogenesis of endometriosis. International journal of reproductive medicine. 2014. https://pubmed.ncbi.nlm.nih.gov/25763392/
- Guerriero S, Ajossa S, Orozco R, Perniciano M, Jurado M, Melis GB et al. Accuracy of transvaginal ultrasound for diagnosis of deep endometriosis in the rectosigmoid: systematic review and meta-analysis. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 2016. https://pubmed.ncbi.nlm.nih.gov/26213903/
- Nisenblat V, Bossuyt PM, Farquhar C, Johnson N, Hull ML Imaging modalities for the non-invasive diagnosis of endometriosis. The Cochrane database of systematic reviews. 2016. https://pubmed.ncbi.nlm.nih.gov/26919512/
- Leonardi M, Uzuner C, Mestdagh W, Lu C, Guerriero S, Zajicek M et al. Diagnostic accuracy of transvaginal ultrasound for detection of endometriosis using International Deep Endometriosis Analysis (IDEA) approach: prospective international pilot study. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 2022. https://pubmed.ncbi.nlm.nih.gov/35561121/
- Becker CM, Bokor A, Heikinheimo O, Horne A, Jansen F, Kiesel L et al. ESHRE guideline: endometriosis. Human reproduction open. 2022. https://pubmed.ncbi.nlm.nih.gov/35350465/
- Vercellini P, Fedele L, Aimi G, Pietropaolo G, Consonni D, Crosignani PG Association between endometriosis stage, lesion type, patient characteristics and severity of pelvic pain symptoms: a multivariate analysis of over 1000 patients. Human reproduction (Oxford, England). 2007. https://pubmed.ncbi.nlm.nih.gov/16936305/
- Vercellini P, Vercellini P, Buffo C, Viganò P, Somigliana E Update on Medical Treatment of Endometriosis: New Drugs or New Therapeutic Approaches?. Gynecologic and obstetric investigation. 2025. https://pubmed.ncbi.nlm.nih.gov/39724866/
- Roman H, Chanavaz-Lacheray I, Hennetier C, Tuech JJ, Dennis T, Verspyck E et al. Long-term risk of repeated surgeries in women managed for endometriosis: a 1,092 patient-series. Fertility and sterility. 2023. https://pubmed.ncbi.nlm.nih.gov/37225069/
- Ianieri MM, Mautone D, Ceccaroni M Recurrence in Deep Infiltrating Endometriosis: A Systematic Review of the Literature. Journal of minimally invasive gynecology. 2018. https://pubmed.ncbi.nlm.nih.gov/29357317/
- Vercellini P, Somigliana E, Daguati R, Vigano P, Meroni F, Crosignani PG Postoperative oral contraceptive exposure and risk of endometrioma recurrence. American journal of obstetrics and gynecology. 2008. https://pubmed.ncbi.nlm.nih.gov/18241819/
- Maddern J, Grundy L, Castro J, Brierley SM. Pain in Endometriosis. Front Cell Neurosci. 2020;14:590823. PMID: 33132854. https://pubmed.ncbi.nlm.nih.gov/33132854/
- Stratton P, Berkley KJ Chronic pelvic pain and endometriosis: translational evidence of the relationship and implications. Human reproduction update. 2011. https://pubmed.ncbi.nlm.nih.gov/21106492/
- Rodríguez-Ruiz Á, Sierra-Artal B, Lozano-Lozano M, Artacho-Cordón F. Impact of Physical Rehabilitation on Endometriosis and Adenomyosis-Related Symptoms: A Systematic Review and Meta-Analysis. J Clin Med. 2025;14(23). https://pubmed.ncbi.nlm.nih.gov/41375589/
- Oosterlynck DJ, Cornillie FJ, Waer M, Vandeputte M, Koninckx PR. Women with endometriosis show a defect in natural killer activity resulting in a decreased cytotoxicity to autologous endometrium. Fertil Steril. 1991. https://rrmacademy.org/library/women-with-endometriosis-show-a-defect-in-natural-killer-activity-resulting-in-a-reczyazlpn2lzrekr/
- Sinaii N, Cleary SD, Ballweg ML, Nieman LK, Stratton P High rates of autoimmune and endocrine disorders, fibromyalgia, chronic fatigue syndrome and atopic diseases among women with endometriosis: a survey analysis. Human reproduction (Oxford, England). 2002. https://pubmed.ncbi.nlm.nih.gov/12351553/
- Endometriosis, Oocyte, and Embryo Quality. https://pubmed.ncbi.nlm.nih.gov/37445220/
- Meyer C, Staib C, Löb S, Altides A, Schwab M, Büchel J et al. Subtype matters: ovarian endometriosis impairs ovarian reserve and embryo quality-should these patients consider fertility preservation?. Archives of gynecology and obstetrics. 2026. https://pubmed.ncbi.nlm.nih.gov/42270946/
- Pittaway DE, Maxson W, Daniell J, Herbert C, Wentz AC Luteal phase defects in infertility patients with endometriosis. Fertility and sterility. 1983. https://pubmed.ncbi.nlm.nih.gov/6840312/
- Nezhat C, Khoyloo F, Tsuei A, et al. The Prevalence of Endometriosis in Patients with Unexplained Infertility. https://rrmacademy.org/library/the-prevalence-of-endometriosis-in-patients-with-unexplained-infertility-recjghj8avxi4uhfq/
Authoritative references
How other clinical authorities define this term. RRM Academy curates these verbatim or under fair use so the medical consensus is visible alongside our RRM-contextualized definition above.
- MeSH D004715
A condition in which functional endometrial tissue is present outside the UTERUS. It is often confined to the PELVIS involving the OVARY, the ligaments, cul-de-sac, and the uterovesical peritoneum.
- NCI Thesaurus C3014
The growth of functional endometrial tissue in anatomic sites outside the uterine body. It most often occurs in the pelvic organs.
- MedlinePlus
Endometriosis is a disease in which tissue like the lining of the uterus grows in other places in your body. These patches of tissue are called "implants," "nodules," or "lesions."
- Wikipedia Endometriosis
Endometriosis is a disease in which tissue similar to the endometrium—the lining of the uterus (womb)—grows elsewhere in the body. The tissue most often grows close to the uterus, such as on the ovaries, fallopian tubes, or the lining of the pelvis.
This content is for educational purposes only and does not constitute medical advice. Consult an RRM clinician or healthcare provider for guidance specific to your situation.
