Chronic Endometritis and Endometriosis: Two Sides of the Same Coin?

Both chronic endometritis and endometriosis are common entities in infertile patients. The association and the co-existence of these two entities are poorly evaluated. The aim of this systematic review and meta-analysis was to examine the association between chronic endometritis and endometriosis and to find the prevalence of chronic endometritis in women with endometriosis. A systematic electronic search was conducted using the MEDLINE, Scopus and Cochrane databases up to May 2022. Observational studies which examined the prevalence of chronic endometritis in women with endometriosis were included. Newcastle-Ottawa Scale was used for the quality assessment. Odds ratios (OR) with 95% confidence intervals (CIs) for dichotomous outcomes and pooled prevalences with 95% CIs were calculated. 855 studies were identified, of which six studies were included in the systematic review and five in the meta-analysis. The prevalence of chronic endometritis in women with endometriosis was 28%, with higher frequency observed in women with endometriosis rASRM stage III-IV (43%) in comparison to women with endometriosis rASRM stage I-II (25%). The meta-analysis showed a significantly higher chronic endometritis in women with endometriosis in comparison to the control group (five studies, 264 endometriosis vs. 435 control, OR = 2.07; 95% CI 1.11-3.84, I$^{2}$ 43%, p = 0.02). The present meta-analysis showed a significantly higher risk of chronic endometritis in women with endometriosis in comparison to the control group. These findings contribute to a better understanding of the causes and consequences of endometriosis and chronic endometritis and may help in the development of more efficient treatment strategies for women with associated infertility.