What is endometritis and does it require treatment?

T he concept of lower genital tract infection with chlamydia or gonorrhoea causing cervicitis and vaginal discharge is familiar to most sexual health physicians. Likewise, upper genital tract infection with inflammation of the fallopian tubes and adnexae in the form of pelvic inflammatory disease (PID) is also a common clinical syndrome with well recognised implications for future fertility. It is assumed that most PID develops secondary to the spread of infection from the lower genital tract, through the uterine cavity into the upper genital tract. What is less certain, and where no clear guidance is currently available, is whether this intermediate step of endometritis is a distinct clinical condition in its own right and, if so, how it should be diagnosed and treated. Endometritis is a pathological diagnosis with infiltration of the normal vascular architecture by inflammatory cells. Agreeing a precise histological definition of endometritis is difficult since a variety of different features are seen—the inflammatory infiltrate may be confined to the surface epithelium or spread more deeply into the stroma; inflammatory cells may comprise neutrophils and/or plasma cells; and lymphoid aggregates or subepithelial haemorrhages have also been reported. The features which correlate most closely to ‘‘true’’ PID are the presence of both neutrophils and plasma cells, leading to the most commonly accepted definition of endometritis which is five or more neutrophils per 400 power field in the superficial endometrium, in addition to one or more plasma cells per 120 power field in the endometrial stroma. Sampling of the endometrium is usually performed using a endometrial suction biopsy device, which is inserted through the cervix to obtain a small piece of endometrial tissue. This is generally a simple, well tolerated procedure performed in an outpatient setting. Unfortunately the fixing, staining, and reporting of the endometrial sample takes several days and even small delays in confirming the diagnosis and starting therapy for pelvic infection can have serious effects on future fertility. This limits the clinical applicability of this approach for making a diagnosis, as does the theoretical risk of introducing infection into the upper genital tract when taking the endometrial biopsy. A more rapid assessment of endometrial inflammation can be obtained by looking at a Gram stained smear or wet mount of vaginal discharge. Increasing numbers of polymorphs in the discharge are associated with endometritis, although the correlation is not particularly strong. The main purpose of looking for pus cells in vaginal secretions lies more in excluding PID than diagnosing it—the negative predictive value of such an approach is around 95%, compared to positive predictive value of only around 20%. In other words the absence of pus cells makes endometritis (and PID) very unlikely, but their presence lacks specificity. Other features on the vaginal smear such as reduced numbers of lactobacilli, may also support the diagnosis of endometritis but have not been rigorously assessed.