Association Between Pelvic Inflammatory Disease and Risk of Endometriosis: A Systematic Review and Meta-Analysis

Background: Endometriosis is a common chronic disorder, which leads to dysmenorrhea, dyspareunia, pelvic chronic pain, and infertility. It affects ∼6% to 10% of the general female population. However, the etiology of endometriosis remained unclear. We aimed to systematically assess the association between pelvic inflammatory disease (PID) and the risk of endometriosis. Materials and Methods: Eligible studies published until May 21, 2022, were retrieved from the PubMed, EMBASE, and Web of Science databases. The studies were included based on the following criteria: (1) original articles on the association between PID and risk of endometriosis; (2) randomized controlled trials and cross-sectional, case-control, and cohort studies; and (3) studies involving humans. The Newcastle-Ottawa Quality Assessment Scale was used to assess the quality of the studies included in this systematic review. The association between PID and risk of endometriosis was evaluated using the overall odds ratio (OR) and correlative 95% confidence interval (CI). Results: The meta-analysis included 14 studies with 747,733 patients. The mean prevalence of PID in women with endometriosis was 33.80%. Our quantitative synthesis revealed that endometritis was associated with a significantly increased risk of endometriosis (OR: 1.63, 95% CI: 1.53-1.74, I² = 59%). Conclusion: We study a statistically significant association between PID and the risk of endometriosis. In particular, endometritis might play an important role in endometriosis, based on the lower heterogeneity of the subgroup analysis. This finding suggests that reducing the incidence of endometritis might aid in the prevention and treatment of endometriosis.