The endometrium is the inner lining of the uterus. When this tissue becomes inflamed, the condition is called endometritis. Chronic endometritis (CE) is a persistent, low-grade inflammatory state that often remains silent, lacking the severe symptoms of an acute infection. This lingering inflammation can interfere with the processes required for successful reproduction. CE is frequently identified only after individuals experience difficulties such as recurrent miscarriages or repeated failed attempts at pregnancy.
Defining Chronic Endometritis and Its Causes
Chronic endometritis is defined by the sustained presence of specific immune cells within the endometrial stroma, indicating a prolonged inflammatory response. It is distinct from acute endometritis, which is a short-lived, symptomatic infection often occurring shortly after childbirth or a gynecological procedure.
The primary cause of CE is an ascending polymicrobial infection, where bacteria travel upward from the vagina and cervix into the uterine cavity. Common causative organisms include a mix of bacteria such as Enterococcus faecalis, Escherichia coli, and Streptococcus, as well as specific organisms like Chlamydia trachomatis or Mycoplasma and Ureaplasma species.
Several factors increase susceptibility to this persistent inflammation. A history of pelvic inflammatory disease (PID) or the presence of an intrauterine device (IUD) significantly raises the risk. Other risk factors include recent gynecological procedures, such as dilation and curettage (D&C), or the retention of tissue following a miscarriage or delivery. Disruption to the normal uterine microbiome, often involving a reduction in beneficial Lactobacillus species, also allows opportunistic pathogens to colonize the endometrium.
Identifying the Clinical Signs
A major challenge in recognizing chronic endometritis is that it frequently produces no noticeable symptoms, leading to its description as a “silent” disease. The condition is often only discovered during an investigation for other reproductive issues. When symptoms do occur, they are often vague and non-specific, overlapping with those of many other gynecological disorders.
Subtle signs sometimes reported include mild, persistent pelvic discomfort or tenderness in the lower abdomen. Abnormal uterine bleeding is another potential indicator, manifesting as spotting between periods, bleeding after sexual intercourse, or unusually heavy menstrual flow. Some individuals may also notice a persistent, unusual vaginal discharge.
CE is most commonly investigated in individuals struggling to conceive. It is found frequently in women experiencing recurrent pregnancy loss (RPL), defined as two or more miscarriages, and in cases of recurrent implantation failure (RIF) during in vitro fertilization (IVF). In these situations, the inflammation is thought to create a hostile environment that prevents the embryo from successfully establishing itself in the uterine lining.
Confirming the Diagnosis
Because CE symptoms are unreliable, a definitive diagnosis requires a tissue sample from the uterine lining. The gold standard is an endometrial biopsy, where a small amount of tissue is collected and sent for analysis. This procedure allows pathologists to examine the tissue’s cellular structure under a microscope.
The hallmark of chronic endometritis is the presence of plasma cells within the endometrial stroma. These white blood cells only appear in the endometrium during a persistent inflammatory or infectious process. To ensure accurate identification, pathologists typically use a specialized technique called immunohistochemistry.
Immunohistochemistry involves staining the tissue sample for the CD138 marker, which is highly expressed on the surface of plasma cells. Using CD138 significantly increases the sensitivity and accuracy of the diagnosis compared to traditional staining methods. A positive result is often defined as the presence of five or more CD138-positive plasma cells in a certain number of microscopic fields.
A physician may also perform a hysteroscopy, inserting a small camera through the cervix to visually inspect the uterine cavity. This procedure can reveal visual clues suggestive of CE, such as endometrial micropolyps or a distinctive “strawberry-like” appearance of the lining. Microbiological cultures or molecular tests, such as PCR, can also be performed on the biopsy sample to identify specific bacterial species, which helps guide treatment.
Treatment Protocols and Reproductive Outcomes
Once CE is confirmed, the standard treatment focuses on eliminating the underlying bacterial infection. This typically involves a 10-to-14-day course of oral antibiotic therapy, often using a broad-spectrum drug like doxycycline. The specific antibiotic chosen may be tailored if the causative pathogen has been identified through culture or molecular testing.
A single course of antibiotics is highly effective, with cure rates often reported to be greater than 80%. However, follow-up testing is necessary to confirm resolution, as the infection can be persistent or recur. A repeat endometrial biopsy, ideally with CD138 staining, is generally recommended after the antibiotic course to ensure the plasma cells are no longer present.
Successful treatment significantly improves the reproductive prognosis for those who previously experienced failures. Curing the inflammation leads to higher subsequent rates of clinical pregnancy and live birth for women with recurrent implantation failure or recurrent pregnancy loss. Resolving the inflammation restores the endometrial lining to a healthy, receptive state, improving the chances of successful embryo implantation.