Pain in Endometriosis

Neurogenic Inflammation in the Context of Endometriosis-What Do We Know?

Endometriosis (EM) is an estrogen-dependent disease characterized by the presence of epithelial, stromal, and smooth muscle cells outside the uterine cavity. It is a chronic and debilitating condition affecting ~10% of women. EM is characterized by infertility and pain, such as dysmenorrhea, chronic pelvic pain, dyspareunia, dysuria, and dyschezia. Although EM was first described in 1860, its aetiology and pathogenesis remain uncertain. Recent evidence demonstrates that the peripheral nervous system plays an important role in the pathophysiology of this disease. Sensory nerves, which surround and innervate endometriotic lesions, not only drive the chronic and debilitating pain associated with EM but also contribute to a growth phenotype by secreting neurotrophic factors and interacting with surrounding immune cells. Here we review the role that peripheral nerves play in driving and maintaining endometriotic lesions. A better understanding of the role of this system, as well as its interactions with immune cells, will unearth novel disease-relevant pathways and targets, providing new therapeutics and better-tailored treatment options.

Evidence for an Association Between Endometriosis and Allergic and Non-allergic Food Hypersensitivity Is Lacking

Endometriosis effects up to 1 in 9 women, and can be a severe and debilitating disease. It is suggested that there is a link between endometriosis and allergic hypersensitivities, including allergic and non-allergic food hypersensitivity. Best practice for managing endometriosis symptoms is holistic and includes broad multi-disciplinary care. Therefore, improving our understanding of common endometriosis comorbidities, including allergic and non-allergic food hypersensitivity, will assist in improving patient quality of life. This mini-review with systematic approach aims to explore the literature for evidence surrounding an association between endometriosis and allergic and/or non-allergic food hypersensitivity from the last 20 years. Of the 849 publications identified, five fulfilled the inclusion criteria. Only one publication reported a statistically significant increased risk for non-allergic food hypersensitivity in patients with endometriosis (P = 0.009), however, the endometriosis group was not uniform in diagnostic criteria and included individuals without laparoscopically visualized disease. No studies elucidated a statistically significant link between allergic food hypersensitivity alone and endometriosis. Therefore, based on a small number of studies with limited research quality, evidence does not support the existence of a link between endometriosis and allergic or non-allergic food hypersensitivity. Sufficiently powered evidence-based research is required, including information which better characterizes the patient's endometriosis symptoms, importantly the gastrointestinal sequalae, as well as specific allergic and non-allergic food hypersensitivities and method of diagnoses. Unequivocally confirming a link between endometriosis and food hypersensitivities is an essential step forward in dispelling the many myths surrounding endometriosis and improving management of disease.

The role of peripheral nerve signaling in endometriosis

A hallmark of endometriosis - a chronic debilitating condition whose causes are poorly understood - is neuronal innervation of lesions. Recent evidence demonstrates that the peripheral nervous system plays an important role in the pathophysiology of this disease. Sensory nerves, which surround and innervate endometriotic lesions, not only drive the chronic and debilitating pain associated with endometriosis but also contribute to a pro-growth phenotype by secreting neurotrophic factors and interacting with surrounding immune cells. The diverse array of contributions that neurons play in endometriosis indicate that it should be considered as a nerve-centric disease. This review is focused on the emerging field of exoneural biology and how it applies to the field of endometriosis, in particular the role that peripheral nerves play in driving and maintaining endometriotic lesions. A better understanding of the mechanisms of neuronal contribution to endometriosis, as well as their interactions with accompanying stromal and immune cells, will unearth novel disease-relevant pathways and targets, providing additional, more selective therapeutic horizons.

Peripheral, Central, and Cross Sensitization in Endometriosis-Associated Pain and Comorbid Pain Syndromes

Endometriosis-associated pain and the mechanisms responsible for its initiation and persistence are complex and difficult to treat. Endometriosis-associated pain is experienced as dysmenorrhea, cyclical pain related to organ function including dysuria, dyschezia and dyspareunia, and persistent pelvic pain. Pain symptomatology correlates poorly with the extent of macroscopic disease. In addition to the local effects of disease, endometriosis-associated pain develops as a product of peripheral sensitization, central sensitization and cross sensitization. Endometriosis-associated pain is further contributed to by comorbid pain conditions, such as bladder pain syndrome, irritable bowel syndrome, abdomino-pelvic myalgia and vulvodynia. This article will review endometriosis-associated pain, its mechanisms, and its comorbid pain syndromes with a view to aiding the clinician in navigating the literature and terminology of pain and pain syndromes. Limitations of our current understanding of endometriosis-associated pain will be acknowledged. Where possible, commonalities in pain mechanisms between endometriosis-associated pain and comorbid pain syndromes will be highlighted.

Endometriosis-associated pain: a review of quality of life, sexual health and couple relationship

INTRODUCTION

Endometriosis is a chronic gynecological disease that affects women's quality of life, sexuality, and relationship. Endometriosis-associated pain plays an essential role in well-being impairment. The present review aimed to analyze literature about endometriosis-associated pain and quality of life, sexual health, and quality of the relationship, assessing the role of the biopsychosocial factors involved and the women's pain experience.

EVIDENCE ACQUISITION

Bibliographic research of relevant articles published from 2015 to 2020 in PubMed, Google Scholar, Web of Science, Scopus, EBSCO, and Cochrane Library.

EVIDENCE SYNTHESIS

Endometriosis is associated with impairing all women's quality of life domains, and pain appears to be the most influential variable. The pain mechanism is not simple and implies several biological, psychological, and social factors. Women's sexual health is also impaired, and patients report dyspareunia, sexual dysfunctions, dissatisfaction, and distress. Partners' sexual well being is compromised as well. Endometriosis negatively influences relationship quality, and the illness burden affects both couple members.

CONCLUSIONS

A multidisciplinary team using a couple-centered and a biopsychosocial approach is crucial to provide appropriate treatment for endometriosis-associated pain. A better comprehension of all bio-psycho-social aspects implicated in women's well-being and pain experience needs more research.