Chronic endometritis — is it time to clarify diagnostic criteria?

Chronic endometritis is a persistent, low-intensity inflammation of endometrial mucosa, characterized by the infiltration of plasma cells into the endometrial stroma This immunological alteration is thought to be a consequence of a bacterial infection. For a long time, chronic endometritis was poorly investigated and rarely considered in clinical practice because it is either asymptomatic or presents with no specific symptoms. Its association with adverse effects on fertility and retrospectively reported effectiveness of antibiotic treatment were the main reasons for a growing interest in this endometrial pathology. Chronic endometritis is now a hot topic in recurrent pregnancy loss and recurrent implantation failure research. Nevertheless, there are still no recommendations to include chronic endometritis investigation in a clinical evaluation of infertile patients. The uncertain role of this condition is an effect of significant differences in study results presented by different research groups. One important reason for these inconsistent findings is a lack of standardised chronic endometritis diagnostic methods. We present a review of the literature, focusing on the currently available chronic endometritis diagnostic techniques. The review is subdivided into three parts concerning the diagnostic accuracy of three main diagnostic modalities. Histopathological examination of endometrial tissue, hysteroscopic evaluation of uterine cavity and identification of the bacterial factor. In conclusion, it is of great importance to establish a consensus on the diagnostic criteria for chronic endometritis. This is the only way to enhance international cooperation and create well-design multicenter studies to evidence the role of this endometrial pathology in infertility.