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.

Background Adenomyosis is a benign disorder defined by ectopic endometrial glands within the uterine myometrium. A study by Mooney et al reported the myometrial‐cervical ratio (MCR), a novel ultrasound measurement that was found to improve the preoperative diagnosis of adenomyosis. Aims To validate the association between sonographic MCR and adenomyosis confirmed on histopathology in an independent patient group. Materials and Methods Single‐centre retrospective cohort study including women who underwent hysterectomy between 1 January 2016 and 31 December 2018 for a benign, non‐obstetric indication with an ultrasound at the study centre prior to surgery. Clinical details and histopathology were extracted. Ultrasound images were reviewed by a gynaecology ultrasound subspecialist blinded to histological findings. Results Eight hundred eighty‐seven patients underwent hysterectomy in the study period for eligible indications; 317 had an ultrasound at the study centre and were included. There was no statistically significant association between the MCR and adenomyosis on histology when all patients were included; however, increased MCR was associated with adenomyosis when those with fibroids on ultrasound were excluded. The area under the receiver operating characteristic for this model was 0.614 (95% CI: 0.53 to 0.69). The optimal MCR cut‐point in this subgroup was 1.79, which achieved 55.6% sensitivity and 62.8% specificity, with 58.5% correctly classified. There was no significant difference in MCR compared to traditional ultrasound markers of adenomyosis. Conclusions In a population undergoing hysterectomy for benign and non‐obstetric indications, the MCR applied to preoperative ultrasound was only weakly associated with a histological diagnosis of adenomyosis.

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