Endometriosis is a gynaecological disease characterised by endometrial-like tissue found external to the uterus, affecting approximately 5-10% of reproductive-aged women worldwide. Patients experience symptoms such as chronic pelvic pain, infertility, dysmenorrhea, and gastrointestinal discomfort, which negatively impact their work productivity, intimate relationships, and social and mental wellbeing. Due to symptoms being poorly characterised and overlapping with other medical conditions, the main challenge of endometriosis is it takes on average 4-11 years for patients to reach a diagnosis, and unnecessary surgeries occur in up to 15-40% of patients. Thus, further studies investigating health indicators, symptoms and clinical characteristics of endometriosis are essential in the development of a simplified and more accurate diagnosis for endometriosis.

This study aims to compare the frequency of common endometriosis lesion types between Indian (540 cases; 540 controls) and Australian (184 cases; 122 controls) endometriosis cohorts and identify and compare menstrual characteristics associated with endometriosis and lesion types. Patient and surgical questionnaire data were collected, and results showed markedly different distributions of lesion types between the two populations (Percentage of Endometrioma (OMA) among cases in Indian: 59.02%; Australian: 29.87%). A significantly higher number of cases experience severe menstrual pelvic pain in both cohorts (Indian: P=1.11e-07; Australian: P=0.022). Period regularity, menstrual bleeding days and early menstrual pelvic pain, were significantly associated with endometriosis and lesion types in the Indian cohort (P<0.05) and individuals with OMA were shown to have fewer menstrual bleeding days compared to individuals with other lesion types in the Australian cohort (P<0.05).

This study suggests there is variation in disease presentation and menstrual characteristics associated with endometriosis between different ethnic populations. Findings highlight the importance of conducting research across ethnic populations and the need to consider effects of ethnicity and/or ancestry when developing clinical guidelines to ensure all women receive appropriate clinical management and care.