Origins, traits, symptoms
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Endometriosis symptoms are different for every patient, and the condition has several potential origins and types. In scientific terms, these two traits mean the condition is heterogenous and multifactorial. Endometriosis may be generally described as endometrial-like glands and stroma occurring outside the uterus, with distinct differences from the endometrium. These tissues have been found throughout the human body, including in the lungs, diaphragm, heart, and other areas. The glands and stroma differentiate endometriosis from endometrial tissue: they are similar, but not the same. Pathology reports from surgical biopsies (tissue samples) are able to distinguish endometriosis from the endometrium. The disease is also characterized by varied responses to therapies: different patients respond differently to similar treatments. An excellent scientific literature review explains these further: The Pathogenesis of Endometriosis: Molecular and Cell Biology Insights, Laganà et al 2019.
Evidence-based definitions: Given the abundance of differential invasive, adhesive, and proliferative behaviors between the native endometrium and the lesions of endometriosis (Delbandi et al 2013), it is not merely just 'rogue' endometrium. The ectopic (note: external to the uterus) lesions of the disease resemble, but are not identical, to their eutopic (note: internal to the uterus) counterparts (Ahn et al 2016). Studies have demonstrated that the tissues are functionally dissimilar (Zanatta et al 2010, Freger et al 2021).
The prevalence of endometriosis has been estimated at 0.9% to 22% overall (Simpson JL 1980, Guo SW 2006), with a recent literature review putting the overall prevalence at 18% (Moradi et al, 2021). The same review found the prevalence levels of endometriosis in women were, respectively: 31% with infertility, 42% with chronic pelvic pain, and 23% asymptomatic.
Origins and Traits
Endometriosis is theorized as resulting from various cells of origin: Müllerian fragments and/or remnants, Müllerianosis (Batt RE, Smith RA, Buck Louis GM, Martin DC, Chapron C, Koninckx PR, Yeh J. Müllerianosis. Histol Histopathol. 2007 Oct;22(10):1161-6) and Mülleriosis (Redwine D commentary on Signorile PG, Baldi F, Bussani R et al. (2009)), endometrial fragments, precursors in fragments and traumatized endometrium, mesenchymal cells, epithelial stem cells, and changes within the uterus.
For both endometriosis and adenomyosis, these cells of origin are then theorized as being disseminated via several potential means: growth by expansion and/or infiltration, embryonic rests in Müllerian areas (vagina and Fallopian tubes, uterus for adenomyosis) and non-Müllerian areas (pelvic area, bowel, lungs, and others). Retrograde menstruation is only one additional potential avenue of dissemination (Wang Y, Nicholes K, Shih IM. The Origin and Pathogenesis of Endometriosis. Annu Rev Pathol. 2020;15:71-95.) It should be noted that the vast majority of people who menstruate (90%) have retrograde menstruation, but only a minority of them develop endometriosis. Also, endometriosis has been found in areas impossible to reach by menstrual reflux, such as on the sciatic nerve: see for instance Laparoscopic morphological aspects and tentative explanation of the aetiopathogenesis of isolated endometriosis of the sciatic nerve: a review based on 267 patients, Possover 2021.
Endometriosis lesions and adenomyosis react to various stimuli, although the extent of reactions differs between patients. Identified stimuli include inflammation, infection (viral and/or bacterial), estrogen, progesterone, and physical trauma (birth, curettage, surgery).
According to Dr Martin DC in his regularly-updated online 'Endometriosis Concepts and Theories': "the transition from normal Müllerian or non-Müllerian stem cells to later forms of endometriosis such as infiltrating endometriosis or ovarian endometrioma appears to hold the most potential for future research and therapeutic options. Transition involves immune modulation, neuroimmune maturation, immunologic dysfunction, immune overload, immune escape, histological, biochemical, reactive, angiogenic, immunological, genetically driven, genetic, gene regulatory (non-hereditary epigenetic), hormonal, and other changes that distinguish late endometriosis from endometrium, Müllerian remnants, or non-Müllerian stem cells."
While pelvic pain is the most recognized symptom for both endometriosis and adenomyosis, it is not always present with the conditions. When pain is present, it does not always correlate to severity or to location of lesions; pain may also be related to other medical issues. With endometriosis, pelvic pain may also occur outside menstruation, whereas with adenomyosis, pain is generally associated with menses: uterine cramps notably.
Other symptoms of endometriosis include low back and/or leg pain, painful bowel movements, changes in bowel and bladder behaviors before and during menstruation, bloating before and during menstruation (often referred to by patients as "endo belly"), fatigue, and infertility or difficulties with fertility.
Pain with breathing and/or shoulder pain particularly during menstruation may indicate diaphragm or lung endometriosis. Pneumothorax and coughing up blood may also indicate endometriosis in the lungs. The non-profit Extrapelvic Not Rare has in-depth descriptions and links to research literature concerning thoracic endometriosis as well as other forms.
Diagnosis and treatments
While current research continues on biomarkers, none have yet been identified as clinically useful. Advances have also been made in MRI and ultrasound to identify endometriosis glands and stroma, as well as adenomyosis, however this is still dependent on operator knowledge and skill, and may not identify all endometriosis or adenomyosis. "Laparoscopy remains the gold standard for diagnosis of endometriosis and using any non-invasive tests should only be undertaken in a research setting"; "No imaging test met the criteria for a replacement or triage test for detecting pelvic endometriosis, albeit TVUS approached the criteria for a SpPin triage test" (Nisenblat et al 2016 regarding biomarkers, and Nisenblat et al 2016 regarding imagery). Adenomyosis can also be diagnosed during laparoscopy or hysteroscopy, which is less invasive than laparoscopy.
Expert, minimally-invasive excision surgery (en français, il s'agit des techniques d'exérèse) remains the gold standard in treatment of both conditions. As noted by Pundir et al 2017, "The limited available evidence shows that at 12 months postsurgery, symptoms of dysmenorrhea, dyschezia, and chronic pelvic pain secondary to endometriosis showed a significantly greater improvement with laparoscopic excision compared with ablation." It does have potential side effects for adhesions (scar tissue) and rare surgical complications. Surgeon availability and skill can make it difficult to access for patients depending on their location; indeed surgical skill is a key aspect in treatment outcomes.
Literature summary by Anna M. Stevenson
This page is a work in progress and will evolve along with research.